Tens of thousands of mourners filled the streets of central Warsaw with red votive candles Saturday night in a display of patriotism and grief hours after President Lech Kaczynski and senior Polish officials were killed when the presidential jet crashed in heavy fog in western Russia. The crash, which officials said killed all 97 people on board, cut a devastating swath through Poland's political and military elite. In addition to Kaczynski and his wife, Maria, the dead included the national bank's president, the deputy foreign minister, the head of the National Security Office, the deputy Parliament speaker as well as lawmakers and presidential aides. Among military personnel killed were the army chief of staff, the head of the air force and the navy chief commander. The tragedy generated what mourners in Warsaw described as a spontaneous outpouring of support, not necessarily for Kaczynski's nationalist politics or his party, but for the office of the presidency and for all those killed alongside him in the service of the nation. 'You can look around the street here, and half the people would not be voting for Kaczynski,' said Aleksander Zborowski, 36, an Arizona State University- educated engineer who was standing in front of the presidential palace along with thousands of other mourners. 'But they are here because he was our president. It is patriotism.' Prime Minister Donald Tusk called the crash 'the most tragic event of the country's postwar history,' and his government called on Poles to observe two minutes of silence. Under Poland's constitution, Tusk exercises primary control over the government, based on his party's majority in Parliament. The president, although the titular armed forces commander, plays a largely ceremonial role. Also listed among the dead were some revered figures in the Polish struggle to break free of communism: Anna Walentynowicz, 80, the diminutive crane operator whose firing in August 1980 from the Lenin Shipyards in Gdansk helped spark the creation of Solidarity, the political movement that nine years later helped topple the communist government; and the last Polish president in exile, Ryszard Kaczorowski, 90, who stepped down when Lech Walesa, the leader of Solidarity, became the first post-communist president of Poland. 'This is a great tragedy, a great shock to us all,' Walesa said. The crash occurred Saturday morning near the city of Smolensk as the president's plane, a 26-year-old Russian-made Tupolev TU-154, was carrying the officials to a ceremony in Russia commemorating the Soviet massacre of Poland's officer corps in 1940 at the outset of World War II, one of the most traumatic events in 20th- century Polish history. The governor of the Smolensk region said the pilot decided to land despite advice from the control tower that he divert to another airport because of poor visibility. The three-engine aircraft clipped trees and broke apart about a mile short of the runway at a military airport, officials said. Television images showed small fires amid the fog and a broken tail fin with the red and white colors of the Polish flag. Kazcynski, who became president in 2005, was the identical twin brother of former Prime Minister Jaroslaw Kaczynski. Together they had roiled domestic and international politics with their combative brand of Polish conservatism that was suspicious of both the Kremlin and the European Union bureaucracy in Brussels. Lech Kaczynski was facing re-election this fall but was trailing in opinion polls. 'In the face of this tragedy, we stand all united,' said Bronislaw Komorowski, speaker of the lower house of Parliament and now the acting president. 'There is no left or right, there are no differences, no divisions. We are all together with our message of compassion to the families of those who died nearby the Smolensk airport.' Komorowski declared a week of national mourning. President Barack Obama, who also telephoned Tusk, said in a statement, 'Our thoughts and prayers are with the Kaczynski family, the loved ones of those killed in this tragic plane crash, and the Polish nation.' Obama said the tragedy was 'devastating to Poland, to the United States, and to the world' and described Kaczynski as 'a distinguished statesman who played a key role in the Solidarity movement and ... was widely admired in the United States as a leader dedicated to advancing freedom and human dignity.' The Polish delegation had been planning to mark the 70th anniversary of the summary execution of more than 20,000 Polish officers by the Soviet Union's secret police, the NKVD, in the forest of Katyn. The spring 1940 massacre followed the division of Poland by Nazi Germany and the Soviet Union at the beginning of World War II. The killings, which were ordered by Soviet dictator Joseph Stalin, were coldly systematic: Each officer was shot in the back of the head, his hands tied behind his back. And by wiping out such a large part of the Polish officer corps, the Soviets created a leadership vacuum they were able to exploit when the Red Army drove the Nazis out of Poland. For decades, the Soviets attempted to cover up the crime, blaming it on the Nazis, and the authorities in Moscow did not accept responsibility until 1990, when Mikhail Gorbachev said the Soviet Union carried out the killings. The legacy of Katyn still festers in Russian-Polish relations, and some in Russia still dismiss the crime as an anti-Russia conspiracy whipped up by the Poles. 'This is unbelievable _ this tragic, cursed Katyn,' Kaczynski's predecessor, Aleksander Kwasniewski, said on Polish television. 'You get chills down your spine.' Russian Prime Minister Vladimir Putin took charge of an investigation into the crash, flying to Smolensk, where he was scheduled to meet Tusk, who flew in from Warsaw. Both men had attended a ceremony this week marking the Katyn massacre, and Putin _ the first Russian leader to attend the commemoration _ said, 'We bow our heads to those who bravely met death here.' James Sherr, head of the Russia and Eurasia program at Chatham House, a London- based think tank, stressed the need for transparency. 'The Russians will be under pressure to handle this in an extremely impressive way, and it is possible, if they can, that the relationship between the countries will benefit,' he said. 'But if the crash and emotions provoked by it lead to recriminations and defensiveness, then we will see something else.' A nationalist with an abiding suspicion of Russia, Kaczynski, 60, did not attend the joint ceremony Wednesday and instead was arriving for a largely Polish ceremony Saturday. Kazcynski had in the past infuriated Moscow with his embrace of Ukrainian and Georgian leaders hostile to Moscow and his support for the placement of a U.S. missile defense system on Polish soil. The deaths near Katyn of Kazcynski and a delegation sprinkled with people who had felt the heavy hand of the Soviets seems extraordinary and will certainly fuel conspiracy theories about the crash. But all early reports pointed to pilot error. Polish and Russian officials said the plane was serviced and refurbished at a Russian plant in December, but the Polish government's continued use of aging Russian jets has been the source of some controversy in the country. The government said it could not afford a new fleet of Western planes. Finn reported from Washington. Special correspondent Karla Adam in London contributed to this report. 