CAIRO — The Egyptian authorities unleashed a ferocious attack on Islamist protesters early Saturday, killing at least 72 people in the second mass killing of demonstrators in three weeks and the deadliest attack by the security services since Egypt’s uprising in early 2011.The attack provided further evidence that Egypt’s security establishment was reasserting its dominance after President Mohamed Morsi’s ouster three weeks ago, and widening its crackdown on his Islamist allies in the Muslim Brotherhood. The tactics — many were killed with gunshot wounds to the head or the chest — suggested that Egypt’s security services felt no need to show any restraint.
“They had orders to shoot to kill,” said Gehad el-Haddad, a Brotherhood spokesman. The message, he said, was, “This is the new regime.”
In Washington, Secretary of State John Kerry called this “a pivotal moment for Egypt” and urged its leaders “to help their country take a step back from the brink.”
The killings occurred a day after hundreds of thousands of Egyptians marched in support of the military, responding to a call by its commander for a “mandate” to fight terrorism. The appeal by Gen. Abdul-Fattah el-Sisi, who has emerged as Egypt’s de facto leader since the military removed Mr. Morsi from power, was widely seen as a green light to the security forces to increase their repression of the Islamists.
In the attack on Saturday, civilians joined riot police officers in
firing live ammunition at the protesters as they marched toward a bridge over the Nile. By early morning, the numbers of wounded people had overwhelmed doctors at a nearby field hospital.
One doctor sat by himself, crying as he whispered verses from the Koran. Nearby, medics tried to revive a man on a gurney. When they failed, he was quickly lifted away to make room for the many others.
With hundreds of people gravely wounded, the toll seemed certain to rise, and by Saturday evening had already surpassed the more than 60 deaths on July 8, when soldiers and police officers fired on pro-Morsi demonstrators.
As the deaths have mounted, more than 200 since the government was overthrown, hopes have faded for a political solution to the standoff between the military and the Brotherhood, whose leaders, including Mr. Morsi, are imprisoned or preparing themselves for jail.
In a televised news conference hours after the clash, Interior Minister Mohamed Ibrahim absolved his men of any responsibility and made no mention of the high death toll. His officers, he said, “have never and will never shoot a bullet on any Egyptian.”
He blamed Mr. Morsi’s supporters for the violence, saying they planned to disrupt traffic on the bridge. “We had to stop them,” Mr. Ibrahim said. The protesters threw rocks and fired weapons, he said, and a large number of officers were wounded, including two who were shot in the head.
Mr. Ibrahim also suggested that further repression was imminent as the authorities prepared to break up sit-ins that thousands of Mr. Morsi’s supporters have held for weeks.
“God willing, it will be dispersed in a way that doesn’t cause many losses,” he said. “But God willing, it must end.”
Mohamed ElBaradei, the Nobel Peace Prize laureate who is vice president in the interim government, added a rare note of support for the Brotherhood from the country’s new leaders, writing on Twitter that he condemned the “excessive use of force” and was trying to “end the standoff in a peaceful manner.”
Mr. Kerry called on Egypt’s leaders to “respect the right of peaceful assembly and freedom of expression” and to open an inclusive political dialogue.
“Over two years ago, a revolution began,” he said in a statement. “Its final verdict is not yet decided, but it will be forever impacted by what happens right now.”
Secretary of Defense Chuck Hagel spoke by telephone with General Sisi, urging him to exercise restraint and “take steps to prevent further bloodshed and loss of life,” according to a Pentagon statement.
The violence broke out on Friday night after a day of large, competing marches by supporters of Mr. Morsi and his opponents expressing solidarity with the military. At least eight people died on Friday, but there was not the kind of widespread violence that many had feared after
General Sisi’s speech on Wednesday calling for demonstrations in support of the military.
That changed around 10:30 p.m., when groups of Mr. Morsi’s supporters left their vast encampment in Nasr City, marching toward the central October 6 Bridge, where police officers were stationed, according to witnesses. Several people said that the protesters had left the camp because it had become overcrowded, and that people had fanned out from the encampment along several boulevards. Others said they had planned to march through a nearby neighborhood.
The group that came under attack walked down Nasr Street, past the reviewing stand where President Anwar el-Sadat was assassinated in 1981, and the pyramid-shaped memorial to the unknown soldier across the street, toward the bridge.
“We didn’t have any weapons,” said Mohamed Abdulhadi, who said he had joined the march, which was “not violent.” More than 10 other witnesses confirmed his assertion.
The Interior Ministry released a video after the killings that it said showed Morsi supporters firing birdshot at the police and damaging property. It showed protesters throwing rocks, unidentified people wandering into traffic, and one man pulling out what appeared to be a silver pistol and firing it, though it is not clear who the man was, or which side of the fighting he was on.
Mohamed Saeed, an agricultural engineer, said he and some of the other protesters had started to exchange words with the officers before even reaching the bridge.
“You know how it is,” he said. “Some of us said some provocative things, and the tear gas started.”
The protesters threw rocks, and the confrontation quickly escalated, Mr. Saeed and others said. The Morsi supporters feared that the police were preparing to storm their encampment, so they started building brick walls on the road to “to prevent them from coming into the sit-in,” Mr. Saeed said.
An hour and a half after the clashes started, the police and their allies started firing live ammunition and pellet guns, Mr. Saeed said. Other witnesses said they had seen snipers on the roofs of nearby buildings.
Ahmed Hagag was there with his best friend, Ashraf. They had rushed to the front line bearing aid for their comrades, but it was useless given the kind of violence under way. “We went there with masks and vinegar,” he said, in preparation for the tear gas.
Ashraf, who had been “yearning for martyrdom,” did not want to stand in the back, Mr. Hagag said. “So it happened, and a bullet ended up in his heart.”
As the sun rose, a bullet struck Mr. Saeed’s right kidney. An hour later, a path that the protesters had cleared to the field hospital had become a highway for the wounded, who came in ambulances, on motorcycles and in the arms of friends.
A taxi drove by with a shattered rear window, pierced by a bullet that struck the driver in the neck. He declined offers of help and kept driving, blood running onto his shirt.
Before the police retreated around 8 a.m., a spray of gunfire had come from their positions, sending people scrambling for cover and setting off a new cavalcade of ambulances.
In the makeshift morgue at the field hospital, 29 bodies lay in a row covered with white sheets. A medic, Mahmoud al-Arabi, said the wounds were disturbing for their accuracy: many of the dead had been shot in their head, chest or neck.
Their shrouds were marked with names and sometimes the cities they had traveled from to join the Islamists in their square: Saadawy Mohamed from Beni Suef, Khaled Abdel al-Nasser from Qena.
Later Saturday, the Health Ministry said 72 people had been killed. The Brotherhood said it had counted 66 dead and classified an additional 61 people as “clinically dead.”
The violence left the Brotherhood in an increasingly dire position, facing the prospect of a ban of the kind it suffered before the uprising against President Hosni Mubarak. Its options at this point are limited, said Samer S. Shehata, a professor of Arab politics at the University of Oklahoma and an authority on the group.
“They really can’t resort to violence,” he said. “They don’t have a militia and it runs against all their rhetoric and recent history.”
Mr. Ibrahim, the interior minister, raised the prospect of a new threat to the Brotherhood, saying Saturday that he was reconstituting a state security agency that under Mr. Mubarak was responsible for monitoring Islamists and known for carrying out torture and forced disappearances. Without security agencies that have a political focus, Mr. Ibrahim said, “the security of the country doesn’t work.”
Robert F. Worth contributed reporting.
This article has been revised to reflect the following correction:
Correction: July 27, 2013
A summary that appeared briefly with an earlier version of this article misstated the death toll. Dozens of people have been killed by the Egyptian authorities, not hundreds.
