Cairo -
Egypt's chief justice Adly al-Mansour was sworn in as interim president on Thursday after the army ousted and detained Mohamed Morsi in an abrupt end to the Islamist's first year in office.
The security forces also began rounding up Morsi's top aides and members of the Muslim Brotherhood movement to which he belongs, a number of sources said.
Morsi's government unravelled on Wednesday after the army gave him a 48-hour ultimatum in the wake of massive demonstrations since June 30 against his turbulent rule.
Mansour took the oath of office at a ceremony in the Supreme Constitutional Court, which was broadcast live on national television.
The swearing-in came after armed forces chief General Abdel Fattah al-Sisi announced Morsi's overthrow on state television late Wednesday, citing his inability to end the country's deepening political crisis.
In his speech, Sisi laid out details of the roadmap for a political transition.
The Islamist-drafted constitution would be frozen and presidential elections held early, he said, without specifying when.
The armed forces, which had deployed troops and armour across the country, would “remain far away from politics,” he stressed.
Mansour, 67, will serve as interim president until new elections are held, according to the army's plan.
Even as Sisi was speaking, the security forces began arresting leading Brotherhood figures, with state media reporting that 300 warrants had been issued.
Saad al-Katatni, head of the ousted president's Freedom and Justice Party, and the Brotherhood's deputy supreme guide Rashad Bayoumi were both arrested and transferred to prison, the official MENA news agency reported.
A judicial source said arrest warrants had also been issued for the Brotherhood's supreme leader Mohammed Badie and his first deputy Khairat El-Shater.
The two are wanted on charges of inciting the killing Sunday of protesters in front of the Brotherhood's headquarters in Cairo's southern neighbourhood of Mokattam, the source said on condition of anonymity.
A senior military officer, meanwhile, told AFP the army was Thursday “preventively” holding Morsi.
The officer, speaking on condition of anonymity, said Morsi might face formal charges linked to his escape, along with other inmates, from prison during the revolt that overthrew dictator Hosni Mubarak in 2011.
Morsi latest arrest came after he issued a defiant call for supporters to protect his elected “legitimacy”, in a recorded speech hours after the military announced his ouster.
“We had to confront it at some point, this threatening rhetoric,” the military officer said.
“He succeeded in creating enmity between Egyptians,” he added.
Morsi's year in power was marked by a spiralling economic crisis, shortages in fuel and often deadly opposition protests.
Thousands of protesters camped out on the streets of Cairo for days celebrated wildly through the night at the news of Morsi's downfall, cheering, whistling, letting off firecrackers and honking car horns.
Egypt's largely state-run press on Thursday unanimously hailed the army's overthrow of Morsi as a “legitimate” revolution.
The main banner in state-owned Al-Akhbar read: “And the people's revolution was victorious.”
Morsi's opponents had accused him of failing the 2011 revolution that toppled Mubarak by concentrating power in the hands of his Muslim Brotherhood.
His supporters say he inherited many problems from a corrupt regime, and that he should have been allowed to complete his term, which had been due to run until 2016.
US President Barack Obama said he was “deeply concerned” over Morsi's ouster and urged the army to refrain from “arbitrary arrests”.
In May, Washington approved $1.3 billion in military aid to Egypt. That was now under review, said Obama, as he called for a swift return to democratic rule.
Germany termed Morsi's ouster by the military as “a major setback for democracy in Egypt”, while Russia called on all Egyptian political forces to “exercise restraint”.
Britain said it will work with Egypt's interim authorities despite not supporting the military intervention that toppled Morsi.
At least 10 people were killed in clashes in Alexandria and in the southern province of Minya during the night, security officials said.
Already in the week leading up to Morsi's downfall, at least 50 people died in clashes between the Islamist's supporters and opponents.
Aside from rounding up members of the Brotherhood, the security forces had shut down broadcasts from the group's television channel, a Morsi aide told AFP. - Sapa-AFP