CAIRO — Islamist Mohammed Morsi promised a “new Egypt” as he took the oath of office Saturday to become the country’s first freely elected president, succeeding Hosni Mubarak who was ousted 16 months ago.

At his inauguration before the Supreme Constitutional Court, Morsi also became the Arab world’s first freely elected Islamist president and Egypt’s fifth head of state since the overthrow of the monarchy some 60 years ago.

He took the oath before the court’s 18 black-robed judges in its Nile-side seat built to resemble an ancient Egyptian temple.

“We aspire to a better tomorrow, a new Egypt and a second republic,” Morsi said during a solemn ceremony shown live on state television.

“Today, the Egyptian people laid the foundation of a new life — absolute freedom, a genuine democracy and stability,” said Morsi, a 60-year-old U.S.-trained engineer from the Muslim Brotherhood, a fundamentalist group that has spent most of the 84 years since its inception as an outlawed organization harshly targeted by successive governments.

“Egypt today is a civil, national, constitutional and modern state,” Morsi, wearing a blue business suit and a red tie, told the judges in the wood-paneled chamber where he took the oath of office. “It is a strong nation because of its people and the beliefs of its sons and its institutions.”