Cairo - Egyptian security forces killed more than 50 supporters of Egypt's ousted president in one of the deadliest single episodes of violence in more than 2.5 years of turmoil.
The toppled leader's Muslim Brotherhood called for an uprising, accusing troops of gunning down protesters, while the military blamed armed Islamists for provoking its forces.
The early morning carnage on Monday at a sit-in by Islamists outside the Republican Guard headquarters, where ousted President Mohammed Morsi was first held last week, further entrenched the battle lines between the ousted president supporters and his opponents.
The uproar weakened the political coalition that backed the military's removal of the country's first freely elected leader.
Egypt's top Muslim cleric, the sheik of Al-Azhar, warned of civil war and took the unusual step of announcing he would seclude himself in his home until the two sides "stop the bloodshed."
The sole Islamist faction that backed Morsi's removal, the ultraconservative Al-Nour Party, suspended its participation in talks on forming a new leadership for the country.
The group is now torn by pressure from many in its base, furious over what they saw as a "massacre" against Islamists.
Both the military and the Brotherhood appeared determined not to back down in the confrontation.
The Brotherhood accuses the military of carrying out a coup against democracy, while their opponents say Morsi squandered his 2012 election victory and leading the country into a Brotherhood monopoly on power.
The Freedom and Justice party, the Muslim Brotherhood's political arm, called on Egyptians to rise up against the army, which it accused of turning Egypt into "a new Syria." The new military-backed leadership, meanwhile, was pushing ahead with its post-Morsi political plans, working on a timetable for new presidential elections and a new Cabinet.
"This could be a moment of extremism for both sides" of the equation, Mohammed Mahsoub, a member of the Islamist Wasat Party told Al-Jazeera TV.
Immediately, both sides presented their versions of what happened at the protest site, where around 1 000 Morsi supporters had been camped out for days in the streets around a Mosque near the Republican Guard Headquarters.
After the violence began around dawn, the two sides battled it out for around three hours.
Protesters and the Brotherhood said it began when troops descended on them and opened fire unprovoked as they finished dawn prayers.
"I was in the last row praying. They were firing from the left and right," said Nashat Mohammed, who had come from southern Egypt to join the sit-in and was wounded in the knee in the mayhem. "We said, 'Stop, we're your brothers. They shot at us from every direction."
Spokespeople for the military and police, however, gave a nationally televised news conference saying gunmen among the protesters sparked the battle.
Army Colonel Ahmed Mohammed Ali said police and troops guarding the Republican Guard complex came under "heavy gunfire" at around 04:00. and attackers on rooftops opened fire with guns and molotov cocktails. A soldier and two policemen were killed, and 42 in the security forces were wounded, eight critically, he said.
While he said troops had a right to defend the facility, however, Ali did not directly explain how the protester deaths occurred. He expressed condolences but offered no apologies for the deaths.
A collection of footage of the clashes provided by the military, aired on Egyptian TV stations, showed protesters on rooftops lobbing projectiles at troops below, including fire bombs and toilet seats. It also showed some armed protesters firing at close range at the troops, but it showed no footage of what the military did.
It was also not clear at what time in the fighting the videos were shot. It included aerial views of the clashes.
Several witnesses from outside the protest said the gunfire started when troops appeared to move on the camp.