Abdel Fattah el-Sisi has promised to "care for the interests of the people" and build a stronger Egypt as he was sworn in as the country's new president.
The former army chief took the oath of office at the Constitutional Court in a suburb south of the Egyptian capital Cairo, the same venue where Mohamed Morsi, the president who he deposed, was sworn in two years ago.
"I swear by almighty God to preserve the republican system, and to respect the constitution and the law and to care for the interests of the people; and to preserve the independence of the nation and its territorial integrity," Sisi said.
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"We will solve the problems of the past and build an Egypt of the future ... Let our differences be the source of enrichment, diversity and giving that add the spirit of cooperation and love to our work.''
Sisi is the fifth Egyptian president to come from the army's ranks. The ceremony also marked the first time one president handed power to the next, although Adly Mansour, the former interim president, was appointed by Sisi.
Sunday was declared a national holiday and tight security was enforced by the police and military throughout Cairo.
"Cairo has announced a state of emergency across its institutions, and no breaks will be taken today and on Sunday," Ahmed Sakr, the deputy governor of Cairo, said on Saturday.
Sisi was declared the country's president last week after winning 96.6 percent of the presidential vote, beating the only other contender, Hamdeen Sabahi, who won 3.09 percent.
Several regional heads of state were among those who attended the ceremony.
Fawaz Gerges, a professor of international relations at the London School of Economics, said that a strong president would be welcomed by many Egyptians who are tired of the upheaval of the last four years.
"Many Egyptians are exhausted. Forty percent live in poverty. They want stability and that is why they voted for Sisi."
An Egyptian court on Saturday sentenced 10 Muslim Brotherhood supporters to death in absentia on charges including inciting violence after the army toppled Morsi last July.
The same court on Saturday postponed until July 5 a verdict in the trial of the Brotherhood's leader, Mohamed Badie, and scores of others for inciting violence.
Badie is being tried in nearly 40 cases, all of which potentially carry the death penalty, and has already been sentenced to death in one case.
Asraf Abdul Ghaffar, a senior member of the Brotherhood, told Al Jazeera that he believed many in Egypt did not recognise Sisi's presidency.
"Sisi is not the president. Morsi has not resigned. The legitimate president is Mohamed Morsi," he said. "Sisi has cracked the Egyptian community."
Source: Al Jazeera and agencies