The head of the Egyptian army has appeared live on television, announcing the suspension of the constitution. General Abdul Fattah Al-Sisi, flanked by religious and military leaders, said the chief justice of constitutional court would take the powers of the presidency.
His announcement means President Mohammed Morsi is no longer in power.
Anti-Morsi protesters in Cairo’s Tahrir Square gave out a huge cheer in response to the speech.
The move follows four days of mass street protests against Mr Morsi, and an ultimatum issued by the military which expired on Wednesday afternoon.
TV stations belonging to Mr Morsi’s Muslim Brotherhood went off air at the end of the speech.
Minutes later, a notice went up on Mr Morsi’s Facebook page denouncing the army move as a “military coup”.
His current whereabouts are unknown, but an unverified tweet urges civilians and members of the military to uphold the law and the constitution.
After Gen Sisi’s address, both Pope Tawadros II – the head of the Coptic Church – and leading opposition figure Mohammed ElBaradei made short statements.
Mr ElBaradei said the new roadmap aimed for national reconciliation and represented a fresh start to the January 2011 revolution.
The army is currently involved in a show of force, fanning out across Cairo and taking control of the capital, BBC correspondent Quentin Sommerville reports.
He described seeing eight armoured personnel carriers heading for Cairo University in Giza, where one of the main pro-Morsi demonstrations was being held.
The tens of thousands of anti-Morsi protesters on the streets of Cairo are now celebrating, with fireworks lighting up the night sky.
But Morsi supporters elsewhere in the city are reported to have shouted: “No to military rule.”