CAIRO (AP) -- Egypt was rocked Monday by the deadliest day since its Islamist president was toppled by the military, with more than 50 of his supporters killed by security forces as the country's top Muslim cleric raised the specter of civil war.
The military found itself on the defensive after the bloodshed, but the interim president drove ahead with the army's political plan. He issued a swift timetable for the process of amending the Islamist-backed constitution and set parliamentary and presidential elections for early 2014.
The killings further entrenched the battle lines between supporters and opponents of ousted President Mohammed Morsi, who was removed by the military July 3 after a year in office following mass demonstrations by millions of Egyptians.
Morsi's Muslim Brotherhood called for an uprising, accusing troops of gunning down protesters, while the military blamed armed Islamists for provoking its forces.
The shootings began during a protest by about 1,000 Islamists outside the Republican Guard headquarters where Morsi, Egypt's first freely elected leader, was detained last week. Demonstrators and members of Morsi's Muslim Brotherhood said 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. "We said, 'Stop, we're your brothers.' They shot at us from every direction."
After a battle lasting about three hours, at least 51 protesters were killed and 435 wounded, most from live ammunition and birdshot, emergency services chief Mohammed Sultan told to the state news agency.
At a nationally televised news conference, Army Col. Ahmed Mohammed Ali said police and troops came under "heavy gunfire" at around 4 a.m. 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, Ali did not directly explain how the protester deaths occurred. He expressed condolences but offered no apologies for the deaths.
A collection of video of the clashes provided by the military to Egyptian TV showed protesters on rooftops lobbing projectiles at troops below, including firebombs and toilet seats. It also showed some armed protesters firing at close range at the troops, but it did not show 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.
University student Mirna el-Helbawi told The Associated Press that she watched from her 14th floor apartment overlooking the scene, after 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 said.
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 were also shooting.
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."
"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.
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.
Reeling from scenes of bloodied protesters in hospitals and clinics, many with gaping wounds, some of Egypt's politicians tried to push new plans for some sort of reconciliation in the deeply polarized nation.
Sheik Ahmed el-Tayeb, the grand imam of Al-Azhar, the most prominent Sunni Muslim institution, demanded that a reconciliation panel with full powers immediately start work and that those detained in recent days be released. Five prominent Brotherhood figures have been jailed since Morsi's fall, and Morsi himself is held in detention in an unknown location.
El-Tayeb's announcement he was going into seclusion was a symbolic but dramatic stance -- a figure seen as a moral compass by many Egyptians expressing his disgust with all sides in the events. Egypt's Coptic popes have at times gone into seclusion to protest acts against the Christian community, but the sheik of Al-Azhar has never done so.