Mohamed Morsi sworn in as Egypt's first popularly-elected president NEW: Mohamed Morsi was sworn in before Egypt's constitutional court A day earlier, Morsi told crowd at Tahrir Square that his authority comes from all Egyptians He vows to help free political prisoners, including man convicted in 1993 World Trade Center blast (CNN) -- Mohamed Morsi was sworn in Saturday as Egypt's first democratically-elected president, taking the helm of a deeply divided nation that is economically strapped and lacks a working government. The historic ceremony took place amid tight security before the Supreme Constitutional Court and was overseen by Egypt's military rulers who have been in control of the country since Hosni Mubarak was ousted last year during a popular revolution. "Today, the Egyptian people established a new life for complete freedom, for a true democracy," Morsi said after taking the oath. "I swear by almighty God that I will uphold the republican system and respect the constitution of the law and look after the interests of the people," he said. Morsi upstaged the ceremony Friday, taking to Cairo's Tahrir Square before thousands and declaring that the people are the source of his authority as president. "The whole nation is listening to me," he said in the televised address. Morsi's speech appeared aimed at Egypt's ruling military council, whose recent actions have raised concerns about whether it would fully hand over control to an elected government. Egypt's electoral commission declared Morsi the president-elect Sunday after a runoff with Ahmed Shafik, a former air force general who served as Mubarak's last prime minister. Morsi had been the candidate of the Muslim Brotherhood's Freedom and Justice Party, but he resigned from the party shortly after he was elected president. Just days before the election, a high court ruled that Egypt's parliament was unconstitutional. Morsi's supporters are pushing for a confrontation with the generals, who following the court ruling ordered the Islamist-dominated parliament dissolved and announced they would retain legislative power for an indefinite time. Additionally, the military rulers named a defense council to oversee national security and foreign policies while also declaring it would maintain control of all military affairs. World leaders, meanwhile, will likely be watching what Morsi does next. During the speech Friday, he said he would work to free the blind Egyptian cleric serving a life sentence in the United States for a conspiracy conviction related to the 1993 World Trade Center bombing. He said he wanted to work to free political prisoners, which he said included Sheikh Omar Abdel-Rahman. "Their rights will be on my shoulders and I won't spare effort" to free them, he said. Morsi is a study in contrasts: a strict Islamist educated in Southern California who vowed during his campaign to stand for women's rights yet argued for banning them from the presidency. During the historic campaign, Morsi said he would support democracy, women's rights and peaceful relations with Israel if he won. But he has also called Israeli leaders "vampires" and "killers." Morsi focused his campaign on appealing to the broadest possible audience after a slogan associated with his campaign, "Islam is the solution," sparked concerns that he could introduce a fundamentalist Islamic theocracy. During the campaign, he said he had no such plans. Asked whether he would maintain Egypt's 1979 accord with Israel, Morsi said, "Yes, of course I will.