By DAVID D. KIRKPATRICK
CAIRO — Egyptian security officers stormed two encampments packed with supporters of the ousted president, Mohamed Morsi, on Wednesday in a scorched-earth assault that killed hundreds, set off a violent backlash across Egypt and underscored the new government’s determination to crush the Islamists who dominated two years of free elections.
The attack, the third mass killing of Islamist demonstrators since the military ousted Mr. Morsi six weeks ago, followed a series of government threats. But the scale — lasting more than 12 hours, with armored vehicles, bulldozers, tear gas, birdshot, live ammunition and snipers — and the ferocity far exceeded the Interior Ministry’s promises of a gradual and measured dispersal.
At least one protester was incinerated in his tent. Many others were shot in the head or chest, including some who appeared to be in their early teens, including the 17-year-old daughter of a prominent Islamist leader, Mohamed el-Beltagy. At a makeshift morgue in one field hospital on Wednesday morning, the number of bodies grew to 12 from 3 in the space of 15 minutes.
“Martyrs, this way,” a medic called out to direct the men bringing new stretchers; the hems of women’s abayas were stained from the pools of blood covering the floor.
Adli Mansour, the figurehead president appointed by Gen. Abdul-Fattah el-Sisi, declared a state of emergency, removing any limits on police action and returning Egypt to the state of virtual martial law that prevailed for three decades under President Hosni Mubarak. The government imposed a 7 p.m. curfew in most of the country, closed the banks and shut down all north-south train service.
The Muslim Brotherhood, the main Islamist group behind Mr. Morsi, reiterated its rejection of violence but called on Egyptians across the country to rise up in protest, and its supporters marched toward the camps to battle the police with rocks and firebombs.
Clashes and gunfire broke out even in well-heeled precincts of the capital far from the protest camps, leaving anxious residents huddled in their homes and the streets all but emptied of life. Angry Islamists attacked at least a dozen police stations around the country, according to the state news media, killing more than 40 police officers.
And they lashed out at Christians, attacking or burning seven churches, according to the interior minister. Coptic Christian and human rights groups said the number was far higher.
The crackdown followed six weeks of attempts by Western diplomats to broker a political resolution that might persuade the Islamists to abandon their protests and rejoin a renewed democratic process despite the military’s removal of Mr. Morsi, Egypt’s first freely elected president. But the brutality of the attack seemed to extinguish any such hopes.
The Health Ministry said that 235 civilians had been killed and more than a thousand others had been wounded across Egypt. But the rate of dead and seriously injured people moving through the field hospitals at the sit-ins seemed to promise the true numbers would be much higher.
The assault prompted the resignation of the interim vice president, Mohamed ElBaradei, a Nobel Prize-winning former diplomat who had lent his reputation to selling the West on the democratic goals of the military takeover.
“We have reached a state of harder polarization and more dangerous division, with the social fabric in danger of tearing, because violence only begets violence,” Mr. ElBaradei wrote in a public letter to the president. “The beneficiaries of what happened today are the preachers of violence and terrorism, the most extremist groups,” he said, “and you will remember what I am telling you.”
The violence was almost universally criticized by Western governments. A spokesman for President Obama said the United States was continuing to review the $1.5 billion in aid it gives Egypt annually, most of which goes to the military. The spokesman, Josh Earnest, said the violence “runs directly counter to pledges from the interim government to pursue reconciliation” with the Islamists.
He said the United States condemned the renewal of the emergency law and urged respect for basic rights like the freedom of assembly and peaceful demonstrations. But he stopped short of writing off the interim government, saying the United States would continue to remind Egypt’s leaders of their promises and urge them “to get back on track.”
Analysts said the attack was the clearest sign yet that the Egyptian police state was re-emerging in full force, overriding liberal cabinet officials like Mr. ElBaradei and ignoring Western diplomatic pressure and talk of cutting financial aid.
“This is the beginning of a systematic crackdown on the Muslim Brotherhood, other Islamists and other opponents of a military coup,” said Emad Shahin, a professor of political science at the American University in Cairo.
“In the end,” he added, “the West will back the winning side.”
The attack began about 7 a.m. when a circle of police officers began firing tear gas at the protest camps and obliterating tents with bulldozers. Although the Interior Ministry had said it would move only gradually and leave a safe exit, soon after the attack began several thousand people appeared trapped inside the main camp, near the Rabaa al-Adawiya mosque, as snipers fired down on those trying to flee and riot police officers with tear gas and birdshot closed in from all sides.
“There is no safe passage,” said Mohamed Abdel Azeem, 25, a wholesaler, who had braved sniper fire to reach a field hospital.
For a time in the late afternoon, the Islamists succeeded in pushing the police back far enough to create an almost safe passage to a hospital building on the edge of what remained of their camp. Only a roughly 20-yard stretch in front of the hospital doors was still vulnerable to sniper fire from above, and a series of Islamist marchers from around the city flowed back into the encampment, bolstering its numbers.
But shortly before dusk, soldiers and police officers renewed their push, and the Islamists were forced at last to flee.
Three journalists were reportedly killed in the fighting: a cameraman for Sky News, the Britain-based news network; a reporter for a newspaper based in the United Arab Emirates; and a reporter for an Egyptian state newspaper. Several others were arrested.
Egyptian state news media played down the violence, reporting that the police were clearing the camps “in a highly civilized way.” In a televised address, Mohamed Ibrahim, interior minister under Mr. Morsi and now under the new government, said his forces “insisted on maintaining the highest degrees of self-restraint.”
Later, state television showed footage of a group of dead bodies it said were discovered under the main stage of the Islamist sit-in, corroborating dark rumors in the anti-Islamist news media. But it appeared to be a gruesome setup: journalists, including a reporter for The New York Times, had visited the area below the stage repeatedly in recent days and found it empty, without any bodies. Although journalists saw at least a few Islamists with guns on Wednesday, there was also no evidence that the Islamists had stockpiled large numbers of weapons inside the camp, as Egyptian state news media had said before the attack.
But in a televised statement, Hazem el-Beblawi, the interim prime minister and a Western-trained economist who had been considered a liberal, cited the Islamists’ supposed stockpiling of weapons and ammunition to argue that the use of force was justified to protect the rights of other citizens.
“Things were spiraling out of control, and we decided to take a firm stance,” he said.
By nightfall the Islamists had established new sit-ins outside a landmark mosque in Cairo and others in cities around the country, defying the new curfew and the interior minister’s vows to break up any such assemblies.
“Is this closer to being resolved tonight than last night?” asked Michael Wahid Hanna, a researcher on Egypt with the New York-based Century Foundation who was visiting Cairo. “Obviously not. I don’t think anybody has thought this through fully.”
Mayy El Sheikh contributed reporting from Cairo, and Alan Cowell from London.
This article has been revised to reflect the following correction:
Correction: August 15, 2013
The list of contributors with an earlier version of this article omitted Alan Cowell, who contributed reporting from London.