At least five were killed in Cairo during clashes overnight between supporters and opponents of Egyptian President Mohamed Morsi.
The number of protesters injured in the riots that began Wednesday evening rose to 350 overnight, according to the state-run Middle East News Agency (MENA).
Thousands of Muslim Brotherhood supporters arrived en masse at the presidential palace, where hundreds of anti-Morsi demonstrators had for days barricaded themselves.
The scene was not much different from that which took place early in the Tahrir Square uprising that in the end, toppled the decades-old regime of former President Hosni Mubarak.
Islamist mobs hurled rocks and firebombs at secular protesters, and the two groups battled in hand-to-hand combat for hours in the area around the palace.
Some anti-Morsi protesters were seen by foreign reporters to have sustained gunshot wounds from pellets and birdshot. But reporters could not determine who had fired what or at whom. And in both camps, some people were swinging clubs.
By 9:30 p.m., Egyptian security forces had given up trying to control the violence and had all but withdrawn, according to an account written by journalist David D. Kirkpatrick, writing for The New York Times.
By Thursday morning, five were dead, according to the Egyptian Ministry of Health, including at least one Islamist.
The country's Vice President Mahmoud Mekke urged both sides to return to “calm dialogue” to consider amendments to a controversial draft Constitution partly responsible for the protests. Three senior ministers resigned, blaming Morsi for the bloodshed.
The anti-Morsi demonstrators have been protesting a recent decree placing his presidential authority above that of the judiciary, and a referendum on the Constitution.
The edict allows the president to remove the chief prosecutor at will, and appoint whoever he wishes instead – which he did immediately following enactment of the decree.
Morsi's first act was to fire the head prosecutor of the Supreme Court, who he had failed to oust a month earlier, and call for renewed investigations into the deaths of 2011 protesters during the January 25 Revolution.
Morsi has also rushed the completion of the writing of the country's new Constitution despite the Assembly having had a deadline extension.
Despite the ire of the Coptic Christian Church, secularist opposition parties, liberals and other non-Islamists, the president has set a national referendum on passage of the document for December 15.