The Egyptian army has installed a top judge of the constitutional court as interim president after placing ousted president Mohamed Morsi under arrest.

Adly Mahmoud Mansour, 67, is expected to be sworn in as president imminently, after his appointment was announced by army chief General Abdul Fattah al-Sisi.

Al-Sisi announced during a televised address that Mansour has been tasked with "running the country's affairs during the transitional period until the election of a new president".

As head of Egypt's High Constitutional Court (HCC), Mansour was one of the key judges in drafting legislation to conduct the presidential elections in 2012 which brought Morsi to power.

Several other Mohammed Brotherhood leaders have also been detained by the army, in addition to their leader. Arrest warrants have been issued for more than 300 members of the Islamist movement.

The top court has also sacked Morsi's prime minister Hisham Qandil and sent him to jail, suspended the newly drafted constitution and pledged to hold fresh elections.

Explaining the coup, al-Sisi said Morsi has "failed to meet the demands of the people".

Thousands of anti-Morsi protesters who have flooded the capital Cairo were jubilant over the latest move, with some demonstrators hailing Morsi's removal a "second revolution" for Egypt.

The United Nations and the western world have not condemned the military's move as a coup, fearing it could force them to impose sanctions on Egypt. However a "deeply concerned" President Barack Obama has urged the country to quickly return to democratic rule.

In contrast, Saudi King Abdullah was quick to congratulate the interim president.

"On behalf of the people of Saudi Arabia I congratulate you for taking over the leadership of Egypt at this critical time in its history," he said.

Syrian President Bashar al-Assad, who has been battling an uprising for over two years, said: "Whoever brings religion to use in politics or in favour of one group at the expense of another will fall anywhere in the world. The summary of what is happening in Egypt is the fall of what is called political Islam," according to the official Thawra daily.