Rome (CNN) -- It was with a call for the protection of the weakest in society that Francis was officially inaugurated Tuesday as the Catholic Church's 266th pontiff, before a crowd of tens of thousands bathed in sunlight. 
 
 Giving his homily before the throngs in St. Peter's Square, Francis showed the humility and concern for ordinary people that have been noted since he became the first Latin American to be elected pope six days ago. 
 
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 Before he spoke, he was given the official symbols of his papacy: a lamb's wool shawl, to represent his role as "the good shepherd," and the Fisherman's Ring, to represent his role of spreading the gospel. 
 
 The ring is not solid gold like that of his predecessors, but made of gold-plated silver -- again reflecting his desire for simplicity. 
 
 The pope delivered his homily in Italian, rooted in a message of looking after the poor and sick, as well as the natural world. 
 
 He reflected first on the symbolism of the date: this is the day that Catholics celebrate the Feast of St. Joseph to honor Jesus' father on Earth, the carpenter Joseph. 
 
 Francis spoke of Joseph's role in protecting not only Jesus and Mary, but also the church. 
 
 He spoke too of the need to protect "all creation, the beauty of the created world" as instructed by the Bible and shown by St. Francis of Assisi, whose name he took as pope. 
 
 This, he said, "means respecting each of God's creatures and respecting the environment in which we live. It means protecting people, showing loving concern for each and every person, especially children, the elderly, those in need, who are often the last we think about." 
 
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 He warned of the consequences if people do not look after one another. 
 
 "Whenever human beings fail to live up to this responsibility, whenever we fail to care for creation and for our brothers and sisters, the way is opened to destruction and hearts are hardened." 
 
 And he urged those in power to live up to their duties, and to all to avoid evil, hatred and pride. 
 
 "I would like to ask all those who have positions of responsibility in economic, political and social life, and all men and women of goodwill: Let us be 'protectors' of creation, protectors of God's plan inscribed in nature, protectors of one another and of the environment," he said. 
 
 Kissing babies 
 
 After his homily, 500 priests dispensed communion to the throngs of locals, pilgrims, tourists and dignitaries gathered for the historic occasion. 
 
 Between 150,000 and 200,000 people turned out in and around St. Peter's Square, said the Rev. Federico Lombardi, a Vatican spokesman. Police in the area told CNN there were fewer people than expected but declined to give an estimate. 
 
 Pope Francis earlier made his way into the square atop an open-top vehicle, spending 17 minutes circling among the crowds in bright sunshine. 
 
 He wore the simple iron cross that he's had since he was appointed bishop and that he had on when he first appeared to the world as pope. And he chose black shoes rather than the red ones favored by Benedict XVI. 
 
 When the gathered faithful held up babies and young children for him to kiss, he obliged. He also stepped out of his sport utility vehicle to kiss the head of a man with a physical disability. 
 
 Even though at least a dozen security officers in suits walked alongside the SUV as he circled the square, his decision to bypass the Popemobile, which his last two predecessors used, was telling. 
 
 The Mercedes Benz G-Class SUV afforded him the kind of direct contact with people he has embraced since becoming pope. 
 
 Had he been in the Popemobile, he would have been behind bulletproof glass, which was installed in 1981 after an assassination attempt on John Paul II. 
 
 Filipino priest and CNN iReporter Joel Camaya, who was among those in St. Peter's Square, was enthralled by the spectacle, and the contrasting humility, of the newly elected pontiff. 
 
 "The Pope spoke with such passion and force that the words exuded life and thus, as he spoke, there were instances of spontaneous applause," he said. "In the piazza, people who haven't even known each other exchanged smiles, happy that they belonged to one big family." 
 
 Francis called his predecessor, Pope Emeritus Benedict XVI, Monday afternoon to wish him well on the day of the Feast of St. Joseph and to thank him again for his service. Benedict, in turn, said he had been following the events since Francis' selection closely and assured his closeness in prayer. 
 
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 Style or substance? 
 
 The Mass which inaugurated Francis as bishop of Rome and marked the official start of his papacy was short, lasting about two hours. This was in keeping with the spirit of simplicity embraced by the new pontiff, the Vatican said before the occasion. 
 
 Francis has already made an impression as a pope of the people who is concerned about the welfare of the poor. But he inherits a church wracked by a decades-old sexual abuse scandal and claims of corruption in the clergy. 
 
 Monsignor Kevin Irwin told CNN the Catholic Church probably would not have to wait long before the changes in style already seen under Francis become changes in substance. 
 
 "It comes down to personnel," he said. "The personnel changes you make in any corporation make all the difference. Leadership matters -- but then who are the other people who help implement his program?" 
 
 The Vatican said Saturday that Francis had provisionally confirmed members of the Vatican hierarchy in their positions, but would take time to reflect before any final appointments are confirmed. 
 
 Irwin said he believes the key changes are likely to come in the late spring or early summer. 
 
 Francis, as a member of the Jesuit order, "gets into things" and is tenacious, he said. "This is a 'take-charge' pope, I would say." 
 
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 World figures 
 
 Back in St. Peter's Basilica, the newly installed bishop of Rome greeted the dignitaries who had flocked from around the world to attend the inauguration Mass. 
 
 President Cristina Fernandez de Kirchner, from Francis' native Argentina, was the first head of state to step up. 
 
 Vice President Joe Biden, leading the U.S. presidential delegation, was also among those to meet the 76-year-old pope, as was Zimbabwe's controversial President Robert Mugabe. 
 
 Mugabe is subject to a European Union travel ban but allowed to visit the continent for religious events and international conferences. 
 
 Vatican Secretary of State Cardinal Tarcisio Bertone -- effectively the Vatican's prime minister -- was at the pope's side as, standing, he gave his greetings for close to an hour and a half. 
 
 The formal encounters over, Francis then went to the barriers around the sides of the basilica to greet priests, nuns and other well-wishers. 
 
 In his first tweet after his inauguration on the @Pontifex account, Pope Francis said: "Let us keep a place for Christ in our lives, let us care for one another and let us be loving custodians of creation." 
 
 He then tweeted again: "True power is service. The Pope must serve all people, especially the poor, the weak, the vulnerable." 
 
 Argentines watch Mass 
 
 Back in Francis' home city, the Argentinian capital, Buenos Aires, the faithful packed the main square to watch the event on large screens set up throughout the Plaza de Mayo. 
 
 According to the state-run newspaper Telam, a telephone call Francis had made from the Vatican was played to all present, saying: "Thanks for the prayers." 
 
 He added, "Let us be aware of one another, care for life, nature, children and old people," before concluding by asking those present to pray for him. 
 
 Groups also gathered in other cities throughout Argentina to watch the early morning Mass, Telam reported. 
 
 The event in St. Peter's Square was attended by 132 delegations from around the world, including six reigning sovereigns and 31 heads of state. 
 
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 Those delegations are among scores from nations and international organizations traveling to the Vatican, led by heads of states and governments. 
 
 European Union leaders Jose Manuel Barroso and Herman Van Rompuy were among those present. 
 
 House Democratic Leader Nancy Pelosi accompanied Biden in the U.S. delegation, the White House said. On Friday, House Speaker John Boehner, a Republican, said he would send a separate bipartisan congressional delegation. 
 
 Cardinal Timothy Dolan of New York, in a letter sent to Francis on Tuesday, offered the "deep affection, prayerful support and sincere pledge of fidelity" of the U.S. bishops and more than 70 million Catholics in the country. 
 
 Also at the Vatican were groups from the Americas, including Brazil, Chile, Mexico and Canada, and from European nations such as Italy, Holland, Belgium and Germany. 
 
 Representatives from across Christianity -- Eastern and Western -- were also present, along with members of other religions, including Judaism, Islam, Buddhism, Sikhism and Jainism. 
 
 This is also one of the busiest times of the year on the Christian calendar, which will mean many public appearances for the new pontiff. 
 
 Less than a week away is Palm Sunday, the holiday that kicks off Holy Week, which culminates in Easter celebrations. 
 
 The Vatican press office said Francis will also have one other task to keep him busy: figuring out "how to answer the millions of e-mail messages that have already been received, despite the fact that he still doesn't have an official address." 
 
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 Hada Messia reported from Rome and Richard Allen Greene from London; Laura Smith-Spark wrote and reported in London. CNN's Ben Wedeman, Ben Brumfield, Marilia Brocchetto, Sarah Brown, Dugald McConnell, Brian Todd, Claudia Rebaza and Jason Hanna also contributed to this report. ||||| VATICAN CITY Pope Francis set the tone for a new, humbler papacy at his inaugural Mass on Tuesday where he called for the Church to defend the weak and protect the environment. 
 
 Addressing up to 200,000 people including many foreign leaders gathered under bright sunshine in St. Peter's Square, the Argentine pope underlined his central message since he was elected by a secret conclave of cardinals last Wednesday - that the Church's mission was to defend the poor and disadvantaged. 
 
 The Mass, formally installing Francis as head of the world's 1.2 billion Roman Catholics, was much simpler and an hour shorter than the baroque splendor of his predecessor Benedict's inauguration in 2005. 
 
 Although he is as conservative doctrinally as Benedict Francis's simpler style and emphasis on the poor marked a sea change from his predecessor that has been widely welcomed by Catholics. 
 
 The first Jesuit pope inherits a Church mired in scandals over priests' sexual abuse of children and the leak of confidential documents alleging corruption and rivalry between cardinals inside the Church government or Curia. 
 
 He has also been accused by some critics in Argentina of not doing enough to oppose human rights abuses under a military government during the 1976-1983 "dirty war" when some 30,000 leftists were kidnapped and killed. The Vatican has denied the accusations. 
 
 In his homily, delivered on the steps of the giant St. Peter's Basilica, Francis, 76, said the Church's mission "means respecting each of God's creatures and respecting the environment in which we live. 
 
 "It means protecting people, showing loving concern for each and every person, especially children, the elderly, those in need, who are often the last we think about." 
 
 The message chimed with the teachings of the 13th century St. Francis of Assisi, from whom the pope took his name and who is a symbol of poverty, simplicity, charity and love of nature. 
 
 In another sign that he wants to maintain a simple life, Francis is still staying at the Vatican hotel where he lived during the conclave and did not move into a suite reserved for him, a spokesman said. It is not clear when he will move into the Apostlic Palace. 
 
 In his homily, Francis said that whenever human beings failed to care for the environment and each other, "The way is opened to destruction and hearts are hardened. Tragically in every period of history there are 'Herods' who plot death, wreak havoc and mar the countenance of men and women." 
 
 OPEN 
 
 Before the Mass, the pope toured St. Peter's Square in an open white jeep, abandoning the bullet-proof popemobile often used by Benedict. 
 
 He stopped frequently to greet those in the huge, flag-waving crowd, kissing babies and getting out to bless a disabled man. 
 
 "He is a simple, humble person, he is not like the untouchable popes, he seems like someone normal people can reach out to," said Argentine electrician Cirigliano Valetin, 51, who works in southern Italy. 
 
 Argentinian Cardinal Leonardo Sandri told Reuters: "For me this is a call to humility and service to others that will mark his papacy... This is a new breeze of fresh air that is blowing through the Church and the name of that breeze is Francis." 
 
 Six sovereigns, U.S. Vice President Joe Biden, Argentine President Cristina Fernandez, other leaders as well as heads of many other faiths were among the 130 delegations. They included Muslim, Jewish, Buddhist, Russian Orthodox and Anglican leaders. 
 
 Francis called for world leaders to be "protectors of one another and of the environment ... Let us not forget that hatred, envy and pride defile our lives. Being protectors, then, also means keeping watch over our emotions, over our hearts." 
 
 For the Mass he wore plain white vestments, trimmed with gold and brown, and black lace-up shoes, in contrast to the stylish red loafers that Benedict wore. 
 
 "We have gone from the rigid theology professor to a teacher of Christian simplicity," said Italian church historian Alberto Melloni, referring to the contrast between the warm, common touch of Francis and Benedict's stiff, intellectual manner. 
 
 The ceremony was shortened to two hours after a three-hour service in 2005 when Benedict began his papacy. The Vatican said Francis later telephoned Benedict to wish him well for Tuesday's feast of St. Joseph, the saint day of the former Joseph Ratzinger. 
 
 FAVOUR 
 
 Before the Mass, Francis collected his newly minted gold ring and pallium, a liturgical woollen band worn around the neck, that had been placed overnight on the tomb of St. Peter under the basilica's altar. 
 
 Hundreds of priests, sheltering from the sun under umbrellas in the Vatican's white and yellow colors, distributed communion to the crowd while Francis watched from a raised throne behind the altar. 
 
 Francis greeted foreign delegations inside the basilica after the Mass. They included Zimbabwe President Robert Mugabe, who has been under a European Union travel ban since 2002 because of allegations of vote rigging and human rights abuses. He was able to travel to the Vatican because it is a separate territory, outside the EU. 
 
 The pope also met Ecumenical Patriarch Bartholomew from Istanbul, the first time the spiritual head of Orthodox Christians has attended a Roman pope's inaugural Mass since the Great Schism between western and eastern Christianity in 1054. 
 
 Before the Mass, Latin America's first pope made a surprise phone call to thousands of his compatriots listening at loudspeakers in the Plaza de Mayo square in Buenos Aires where they had gathered hours before dawn to watch the celebrations on large television screens. 
 
 In his message, at 3.30 a.m. (0630 GMT), the former Buenos Aires Cardinal Jorge Bergoglio thanked the crowd for their prayers "which I need a lot". 
 
 "I want to ask you a favor, that we walk together, that we look after each other... Don't forget this bishop who, though far away, cares so much for you," he said. 
 
 In the United States, a Reuters/Ipsos poll found 85 percent of those who said they were aware of the new pope had a favorable view of him, including 94 percent of Catholics. 
 
 Two-thirds of U.S. adults, including 9 out of 10 Catholics, expect him to be a good leader of the Catholic Church. 
 
 About 50 percent, however, said they would have liked to see someone younger elected. 
 
 (Writing by Barry Moody and Philip Pullella; Editing by Louise Ireland and Robin Pomeroy) ||||| The son of Italian immigrants to Argentina, Francis is the first pope from Latin America. Before the installation Mass, he called his native country, and his voice was broadcast in the Plaza de Mayo in Buenos Aires, to the delight of the crowds that had maintained an all-night vigil awaiting the Mass from the man they had known as Cardinal Jorge Mario Bergoglio. 
 
 Francis is also the first Jesuit pope; the order is based on service, and its members have traditionally shunned climbing the church hierarchy. In his homily, Francis quoted Scripture to say that as bishop of Rome, he was endowed with “a certain power.” But he added, “Let us never forget that authentic power is service.” 
 
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 “He must be inspired by the lowly, concrete and faithful service which marked St. Joseph,” Francis said during the Mass, which fell on the Feast of St. Joseph. “He must open his arms to protect all of God’s people and embrace with tender affection the whole of humanity, especially the poorest, the weakest, the least important, those whom Matthew lists in the final judgment on love: the hungry, the thirsty, the stranger, the naked, the sick and those in prison.” 
 
 Francis’ reference to St. Joseph could also be interpreted as a signal to Benedict XVI, the pope emeritus and former Cardinal Joseph Ratzinger, whose decision to step down last month shook the Catholic world. On Tuesday, Francis sent his predecessor a warm greeting “full of affection and gratitude,” drawing long applause from the crowd. The Vatican said Tuesday that Francis had also called Benedict to wish him a happy name day, and offered “his and the church’s thanks for his service.” It called the conversation “broad and cordial.” 
 
 The Vatican statement said that “Benedict followed the events of these days with intense participation,” including the installation Mass, “and assures his successor his continued closeness in prayer.” 
 
 About 150,000 to 200,000 people attended the Mass, the Vatican said. As it began, Francis received two symbolic emblems of his role as leader of the world’s 1.2 billion Roman Catholics: the fisherman’s ring, which recalls how St. Peter fished for food and later for souls, and the pallium, a white woolen vestment decorated with red crosses that symbolizes the role of the pope as a good shepherd. 
 
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 “Let us not forget that hatred, envy and pride defile our lives,” Francis said in his homily. “We must not be afraid of goodness or even tenderness,” he added. 
 
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 His words resonated with Andreina Baldi, 58, a housewife from Rome who attended the Mass. “This is why we are all here, his warmth,” she said. “He just said that we should all open our arms to welcome God’s people, anybody, the poor, the youngest, those in jail. And he is already doing so.” 
 
 Anna Di Renzo, an artist from the northern Italian village of Portacomaro, the ancestral home of Francis’ family, said, “In just a few days, he has conquered our hearts.” 
 
 The Vatican said that representatives of 132 countries and international organizations were to attend the Mass. They included Robert Mugabe, the autocratic president of Zimbabwe. He is the subject of a travel ban by European countries because of Zimbabwe’s human rights record. The Vatican has said that it does not issue invitations but welcomes leaders who come. 
 
 In St. Peter’s Square, Brother Gregory Lucrezia of the Franciscan Friars of the Atonement, originally of Garrison, N.Y., said he hoped that under Francis, the Catholic Church would return to a mission of service. “I don’t think he’ll solve everyone’s problems, because they are many and deep, but his prayerful attitude and ability to unite everyone” should go a long way, he said.
– Pope Francis officially kicked off his papacy today with a call to protect the planet and its poor, in a "low-key" yet dignitary-stuffed inaugural Mass that installed him as the Catholic Church's 266th pontiff. “Let us never forget that authentic power is service and that the pope, too, when exercising power, must enter ever more fully into that service which has its radiant culmination on the Cross," he told the crowd in St. Peter's Square. His inauguration was a simpler—and shorter—affair than previous ones, Reuters reports. In a sign of the humble and open style the Argentine is expected to bring to the papacy, he shunned the bullet-proof popemobile to tour the square in an open-topped Jeep, emerging to walk among the crowd, shaking hands and kissing babies. As the service began, he received the fisherman's ring that symbolizes the papacy and the white woolen vestment that symbolizes his role as a shepherd for the faithful, the New York Times reports. The square holds around 100,000 people but Italian authorities were predicting the crowd in the area would top 1 million, CNN reports. The service installing Francis was attended by 132 official delegations and religious leaders from around the world, including six sovereign rulers, 31 heads of state, three princes, and 11 heads of government, mostly from Latin America, the AP reports. The pope will meet the government delegations in St. Peter's Basilica following today's service and meet with religious delegations from around the world tomorrow before taking a day off. Reuters adds that Francis surprised his native Argentina with a phone call home.