Egypt’s prosecutor’s office has ordered the arrest of the leader of the Islamist Muslim Brotherhood movement, Mohammed Badie, state media report.
Mr Badie is accused of inciting the violence in Cairo on Monday in which
at least 51 people were killed.
Several leading Brotherhood figures are already in detention and warrants have been issued for hundreds more.
It comes as the interim prime minister attempts to form a government after the overthrow of President Mohammed Morsi.
The Muslim Brotherhood, which Mr Morsi comes from, say his ousting by the army amounts to a coup.
Its supporters have been staging large protestsat the Rabaa al-Adawiya mosque in the capital,demanding his release from detention and reinstatement.
The movement’s political wing, the Freedom and Justice Party (FJP), had already said it would not accept an offer to join the cabinet being set up by Prime Minister Hazem al-Beblawi.
Correspondents say the arrest warrants could scupper any attempts to persuade the Brotherhood to participate in the transitional political process.
Spokesman Gehad El-Haddad told Reuters the charges against Mr Badie and other senior leaders were “nothing more than an attempt by the police state to dismantle the Rabaa protest”.
He said some of those wanted by the authorities were at the protest.
There were conflicting reports about what happened in Monday’s violence.
The Brotherhood maintains that the army opened fire as protesters were holding dawn prayers outside the Presidential Guard barracks where they believe he is being held.
But the army said troops had responded after coming under attack from armed assailants.
More than 50 Brotherhood supporters and at least one soldier were killed.
The previous Friday, Mr Badie had appeared at a rally there, telling the crowd: “We shall stay in the squares until we bring President Morsi back to power.”
He said their protests would remain peaceful and called on the army not to “direct your armsagainst us”.
The BBC’s Jim Muir, in Cairo, says the protest now covers several square kilometres of the capital, and to clear it out forcibly would almost certainly involve further bloodshed.
There is a feeling among the protesters that they have returned to the situation they were in under former President Hosni Mubarak, when the movement was banned and its members hunted down, says our correspondent.
The timetable for new elections, announced byInterim President Adly Mansour on Monday evening, laid out plans to set up a panel to amend the suspended Islamist-drafted constitution within 15 days.
The changes would then be put to a referendum – to be organised within four months – which would pave the way for parliamentary elections, possibly in early 2014.
Once the new parliament convenes, elections would be called to appoint a new president.
A spokesman for Mr Mansour said posts in the cabinet would be offered to the Brotherhood’s political wing the Freedom and Justice Party (FJP), which won Egypt’s first free elections.
But Mohamed Kamal, a senior official in the FJP, told the BBC: “We will never take part in any cabinet as long as Morsi is not back as a president.”
The party’s deputy chairman, Essam al-Erian, earlier called the election timetable “a constitutional decree by a man appointed by putschists”.
The liberal coalition National Salvation Front (NSF), which organised the protests that ended Mr Morsi’s time in office, has expressed its reservations about the decree, saying it was not consulted.
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