The carnage outside the Republican Guard building in Cairo -- where toppled President Mohammed Morsi was first held last week -- marked the single biggest death toll since massive protests forced Morsi's government from power and brought in an interim civilian administration.
Even before all the bodies were counted, there were conflicting accounts on how the violence began. The pro-Morsi protesters said the troops attacked their encampment without provocation just after they had performed dawn prayers. The military said it came under a heavy assault first by gunmen who killed an army officer and two policemen, though its account of the events left many questions unanswered.
Witnesses from outside the protest camp said troops appeared to be moving to clear the days-old sit-in and were firing tear gas when gunfire erupted. One said she believed the fire came from the protesters' side, though others could not tell.
Whatever the spark, clashes went on for three hours, with protesters hurling stones and molotov cocktails from rooftops and gunshots ringing out. Nearby clinics run by Brotherhood supporters were swamped by wounded protesters, some with gaping, bleeding wounds. More than 400 were wounded in the mayhem, officials said.
The violence is almost certain to draw sharper battle lines between Morsi's Muslim Brotherhood, who say the military has carried out a coup against democracy, and their opponents, who claim Morsi squandered his 2012 election victory and was wrecking democracy by bolstering his and the Brotherhood's grip on the state.
In a move that is likely to further inflame the situation, the Freedom and Justice party, the Muslim Brotherhood's political arm, called on Egyptians to rise up against the army. Morsi has been a longtime leader of the Brotherhood.
The party also called on the international community to stop what it called the massacres in Egypt and accused the military of pushing Egypt toward civil war, warning the country was in danger of becoming a "new Syria."
"The only thing the military understands is force and they are trying to force people into submission," said Marwan Mosaad, speaking at a field hospital run by Morsi's supporters. "It is a struggle of wills and no one can predict anything."
The bloodshed opened cracks in the grouping of movements that backed the military's removal of Morsi.
Egypt's top Muslim cleric warned of "civil war" and said he was going into seclusion until the violence ends -- a rare and dramatic show of protest directed at both sides. He demanded a process immediately be set up for reconciliation, including the release of Brotherhood detainees.
Sheik Ahmed el-Tayeb, head of Al-Azhar Mosque, said he had "no choice" but to seclude himself at home "until everyone shoulders his responsibility to stop the bloodshed instead of dragging the country into civil war."
The ultraconservative Al-Nour Party, the sole Islamist party that had joined talks on a new government and a post-Morsi political process, announced it was suspending its support for the transition plan in response to the "massacre."
The party was struggling whether to fully bolt from the new leadership in the face of a possible revolt by its own members angry over what they see as a a massacre against fellow Islamists. One lawmaker from the party said it's unclear how long party leaders can keep their control, with some members breaking ranks to join the Brotherhood. The lawmaker spoke on condition of anonymity to discuss the group's internal situation.
In a statement, Al-Nour and the Dawa Salafiya, its parent group of hard-line clerics, issued a statement saying the military's response in the violence was "exaggerated." It denounced what it called incitement against fellow Islamists and appeared to be trying to find a compromise stance short of outright breaking ranks with the post-Morsi leadership.
Speaking to Al-Jazeera TV, the party's chief Younes Makhyoun raised the possibility of calling a referendum on Morsi.
Pro-reform leader Mohamed ElBaradei, a top secular and liberal figure who backed the military's removal of Morsi, condemned the violence and called for an investigation, writing on Twitter that "peaceful transition (is) the only way."
The escalating chaos will also further complicate Egypt's relations with Washington and other Western allies, which had supported Morsi as the country's first freely elected leader and now are reassessing policies toward the military-backed group that forced him out. Still, the White House said Monday that cutting off the more than $1 billion in annual aid to Egypt was not in the U.S.'s best interests, though it was reviewing whether the military's moves constitute a coup -- which would force such a measure under U.S. law.
The morning's violence left at least 51 protesters dead and 435 wounded, most from live ammunition and birdshot, emergency services chief Mohammed Sultan, according to the state news agency. Two policemen and one soldier were also killed, according to the military.
The Morsi supporters had been camped out for days at the site in tents around a mosque near the Republican Guard complex, where Morsi was initially held but was later moved to an undisclosed Defense Ministry facility.
Spokesmen for the military and police gave a nationally televised press conference to give their version of the morning's bloodshed.
Army Col. Ahmed Mohammed Ali said police and troops guarding the Republican Guard complex came under "heavy gunfire" at around 4 a.m. and attackers on rooftops opened fire with guns and molotov cocktails. Along with the soldier and two policemen, 42 in the security forces were wounded, eight critically, he said.
He underlined that the troops had the right to defend the installation and that the protest "was no longer peaceful." He pointed out that suspected Islamists have carried out coordinated armed attacks on several military facilities in recent days in the Sinai Peninsula.
One witness, university student Mirna el-Helbawi, watched from her apartment overlooking the scene, prompted when she heard protesters banging on metal barricades, a common battle cry. El-Helbawi, 21, said she saw troops and police approaching the protesters, who were lined up on the street behind a make-shift wall. The troops fired tear gas, the protesters responded with rocks, she told The Associated Press.
Soon after she heard the first gunshots and saw the troops initially retreat backward -- which she said led her to believe the shots came from the protester side. She saw Morsi supporters firing from rooftops, while the troops also opened fire.
Supporters of Morsi, however, said the security forces fired on hundreds of protesters, including women and children, at the sit-in encampment as they performed early morning prayers.
"They opened fire with live ammunition and lobbed tear gas," said Al-Shaimaa Younes, who was at the sit-in. "There was panic and people started running. I saw people fall."
A Muslim Brotherhood spokesman, Mourad Ali, denied any Morsi supporters fired first and said the military had warned protesters it will break up the sit-in.
Abu Ubaida Mahmoud, a religion student from Al-Azhar University, said he had been praying when the sit-in's security teams began banging on metal barricades in warning. He then saw troops coming out of the Guard complex.
"The number of troops that came from inside was stunning," said Mahmoud, who was wounded in the hand. The troops opened fire and "I saw injuries in the chest, the neck, the head and the arm," he said.
A guard at a nearby bank said security forces first moved in on the encampment firing tear gas, then he heard gunfire, though who couldn't tell who was firing. He said that over recent days the Morsi protesters had imposed their control on the surrounding district and were clearly armed.
At field hospitals set up by Morsi supporters, at least six dead bodies were shown laid out on the ground, some with severe wounds, in video aired by Al-Jazeera TV. The bodies had been draped with an Egyptian flag and pictures of Morsi. Pools of blood covered the floor and doctors struggled to deal with gaping wounds among some of the hundreds injured.
Egyptian state TV showed images provided by the military of the scene of the sit-in amid the melee. Dozens of protesters were shown pelting troops with rocks and setting tires on fire. Soldiers in riot gear and carrying shields formed lines a few meters (yards) away.
A fire raged from an apartment in a building overlooking the clashes. Images showed men throwing spears from atop nearby building rooftops. Other protesters were lobbing fire bombs at the troops. It was not clear at what stage in the melee the footage was filmed. Security officers were showing cameras bullet casings, and troops were carrying injured colleagues.
By the afternoon, the sit-in site was cleared along with blockades that had been set up on roads. The site of the early morning clashes, a strip of road about a kilometer long (about half a mile), was covered with rocks, shattered glass, shoes, clothes, prayer rugs and personal photographs. A big Morsi banner remained hoisted in front of the Republican Guards' building. On the ground below it, graffiti read: "Where are our votes?"
Interim President Adly Mansour ordered a judicial inquiry into the killings. Significantly, the statement from his office echoed the military's version of events, noting that the killings followed an attempt to storm the Republican Guard's headquarters.
Prosecutors in Cairo also ordered the closure of the Brotherhood party's headquarters amid investigations into a cache of weapons found there, according to the official Middle East News Agency.
Morsi supporters have been holding rallies and a sit-in outside the Republican Guard building and elsewhere around Cairo since the military deposed Morsi on Wednesday. The military chief replaced Morsi with an interim president until presidential elections are held. The transition plan is backed by liberal and secular opponents of Morsi, and had been also supported by the Al-Nour Party and Muslim and Christian religious leaders.
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