Egypt's Muslim Brotherhood was left reeling last night after the army pledged to intervene in the country's political crisis in 48 hours if the government it leads could not reach a compromise with opposition forces filling the capital's streets.
The unprecedented step, described by government opponents as a "coup with two days' notice", left the Islamist organisation looking beaten and outnumbered just a year after it won election.
Fearing that President Mohammed Morsi was no longer capable of controlling the country, the army issued a statement in response to the huge protest marches and violent clashes that have swept Cairo and other cities.
"The armed forces repeat their call to respond to the people's demands, and give everyone 48 hours as a last chance to fulfil the burden of historical circumstance," the statement, signed by Gen Abdulfatah al-Sisi, the minister of defence and head of the armed forces, said.
"If the demands of the people are not met within this period, it will be incumbent upon us to announce a road map for the future and oversee measures to implement it."
The announcement appeared to stun the Brotherhood and supporters of Mr Morsi, who, until the marches were launched on Sunday, were confident that only a minority of people supported opposition calls for him to quit.
There was no sign that he had been informed in advance of the army's move, even though Gen Sisi is a member of Mr Morsi's cabinet.
It is not clear that it means the army will force Mr Morsi to step down – or whether he would do so if it was demanded of him. He was said to be meeting Gen Sisi and to be preparing to give his own response last night.
But many of the protesters on the streets believed the army would at least order fresh elections – a key demand.
Tamarod, or "Rebellion", the opposition coalition that organised Sunday's protests, said the army had "sided with the people".
The announcement was met with cheers by tens of thousands gathered in Tahrir Square.
In tumultuous scenes, drivers in Cairo honked their horns and waved national flags out of their windows.
Earlier, some protesters had turned their attention to the Brotherhood headquarters in the new development of Moqattam on the edge of Cairo.
The police had refused to defend the property, and in the clashes that ensued gunshots were exchanged. Eight people, all protesters, were killed.
At their own semi-permanent counter-rally outside the Rabaa al-Adawiya mosque, Brotherhood supporters said they had been betrayed and urged Mr Morsi not to step aside. (© Daily Telegraph, London)