The head of the Egyptian army appeared live on television late on Wednesday night, announcing the suspension of the country’s constitution, the BBC reported.
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 Morsi, and an ultimatum issued by the military which expired on Wednesday afternoon.
After General Sisi’s address, both Pope Tawadros II, the head of the Coptic Church, and leading opposition figure Mohammed ElBaradei made short statements.
ElBaradei said the new roadmap aimed for national reconciliation and represented a fresh start to the January 2011 revolution.
TV stations belonging to Morsi’s Muslim Brotherhood went off air at the end of the speech.
Earlier, the country’s top generals summoned civilian political leaders to an emergency meeting on Wednesday to discuss a new interim government while moving tanks toward the presidential palace and restricting Morsi’s travel.
The developments followed as street tensions intensified and a 48-hour deadline imposed by the military generals on the increasingly isolated president to meet the demands of millions of unhappy Egyptians came and went.
By 6:30pm military forces began moving around Cairo. Tanks and troops headed for the presidential palace – although it was unclear whether Morsi was inside – while other soldiers ringed the nearby square where tens of thousands of the president’s supporters were rallying.
Many of the Islamists had armed themselves with makeshift clubs, shields made of pot covers or metal scraps and plastic hard hats, and there were small scuffles with the better-armed soldiers. Some soldiers fired their weapons in the air. But the military forces held back.
Morsi’s senior foreign policy adviser, Essam el-Haddad, issued an open letter on Wednesday on his official Web page lamenting what he called the imminent takeover of Egypt’s first freely elected government.
“As I write these lines I am fully aware that these may be the last lines I get to post on this page,” he wrote. “For the sake of Egypt and for historical accuracy, let’s call what is happening by its real name: Military coup.”
Security officials said the military’s intelligence service had banned any travel by Morsi and senior Islamist aides, including the Muslim Brotherhood’s supreme guide, Mohamed Badie, and his influential deputy, Khairat el-Shater.
People close to the president said at around the same time that talks with the generals continued but looked increasingly futile.
With millions of Egyptians waiting to see what the military would do, Morsi reiterated in a Facebook posting what he had said in a long televised speech Tuesday night, vowing to stay in power as Egypt’s first democratically elected president following the 2011 revolution that overthrew Hosni Mubarak.
“The presidency reaffirms that violating constitutional legitimacy threatens democratic practice by veering off the right track and threatens the freedom of expression that Egypt has lived since the revolution,” the statement said.
Among those called to the meeting with the generals was Mohamed ElBaradei, the former UN diplomat who has been tapped by the protesters demanding Morsi’s ouster as one of their negotiators over a new interim government.
ElBaradei has been an outspoken critic of Morsi and his allies in the Muslim Brotherhood, the constitution they pushed to a referendum and the previous period of military rule.