"I swear to uphold the republican system and respect the constitution and the law," said al-Sisi, taking the oath of office on Sunday.

The new president was sworn in by members of the Supreme Constitutional Court.

Outgoing interim President Adly Mansour, who now returns to his old post as head of the Supreme Constitutional Court, stood beside al-Sisi.

Al-Sisi, who had resigned his post as army chief to enter the presidential poll, has been officially declared Egypt's new president after winning almost 97 percent of the vote, according to Egypt's military-installed election commission.

The vote was the second milestone of a transitional roadmap imposed by the army after its ouster of the nation's first elected president Mohammad Morsi on July 3 following mass protests against his one-year rule.

With the swearing-in ceremony concluded, al-Sisi starts a four-year presidential term.

Apart from public activities expected to be held across the country to celebrate the inauguration of a new president, al-Sisi will attend two major activities later on Sunday in Cairo.

The new president will host a reception in honor of Arab and foreign dignitaries attending his inauguration, including Lebanon's Speaker Nabih Berri.

Later in the evening, a special celebration will be organized by the presidency for Egyptian dignitaries.

Al-Sisi is expected to deliver during the celebration his first official national address outlining his priorities as president.

Al-Sisi starts his tenure while the populous Arab country faces numerous economic, political and security challenges.

NTJ/MB