Egyptian Chief Justice Adli Mansour was sworn in the country's interim president Thursday, hours after the army ousted incumbent Mohammed Morsi and put him under house arrest. The army was detaining other part leaders till evening.
Mansour, who took oath as head of the Supreme Constitutional Court (SCC) earlier in the day, said fresh elections were "the only way" forward. But he gave no indication of when these would be held, BBC reported.
Morsi, the country's first freely-elected leader, described the political developments as a military coup. The army, though, said Morsi had "failed to meet the demands of the people".
Protestors accused Morsi and his party, Muslim Brotherhood, of carrying out an Islamist agenda and failing to tackle Egypt's economic problems.
At least 10 people were killed and scores injured in clashes across the country. Some 50 people have died since the latest unrest began Sunday, according to the health ministry.
Late Thursday, Egypt's military moved against the leadership of the Muslim Brotherhood.
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Morsi was being detained, as well as senior figures in the Islamist group of which he is a member. Hundreds more are being sought, BBC reported.
Gehad el-Haddad, a spokesperson for the Muslim Brotherhood, earlier said Morsi had been put under house arrest and the "entire presidential team" was in detention.
Haddad's father, senior Morsi aide Essam el-Haddad, and Saad al-Katatni, head of the FJP, were among those being held.
Meanwhile, Morsi's Muslim Brotherhood party rejected "a military coup" against the ousted president and denounced it.
"We reject working with the current usurping authority and we denounce the violent dealing with (pro-Morsi) peaceful protestors," Xinhua reported the group as stating on its website.
It also criticised "the practices of the police repressive state", referring to the closure of Islamic TV channels and the arrests of their crew as restriction of freedom of expression.
The statement referred to Morsi as "the President of Egypt", quoting his previous speech in which he described the army's recent procedures as "a complete military coup".
The statement came in the wake of the ouster of the Islamist-oriented president by the military Wednesday after he failed to respond to millions of protesters staging demonstrations on the streets to seek its ouster and calling for holding early presidential elections.