CAIRO -- Protesters threw incendiary devices over the walls of Egypt's presidential palace during Friday demonstrations against President Mohamed Morsi, leading to clashes with riot police officers that filled the area with tear gas and threatened to deepen Egypt's spiraling political crisis.
The violence drew a quick condemnation from Mr. Morsi, who blamed unnamed "political forces" for inciting what he said was an attempt to "storm the gates of the palace." He promised that the security forces would respond "decisively."
"We stress that such violent practices have nothing to do with the principles of the revolution or legitimate means of expression," said his statement on Twitter. "We hold political forces that might have incited such violent actions fully responsible until results of the investigation are known."
The statement also called on "patriotic forces" to denounce the violence and "urge their supporters to immediately withdraw from the palace area."
The clashes started after a peaceful anti-government sit-in that lasted several hours outside the palace walls. As night fell, a small group of protesters threw incendiary devices over a palace gate, while officers inside fired a water cannon back, to disperse protesters but also to douse small fires, including one that started on a guardhouse by the gate.
On a broad avenue in front of the palace, armored carriers advanced, firing heavy amounts of tear gas and driving the protesters back. Security officers set fire to tents the protesters had set up across the street from the palace, and threw protest banners on small fires that were lit in the streets.
The clashes came after a week of violence in several Egyptian cities that left more than 50 people dead, leading Egypt's defense minister to warn of the potential "collapse" of the state.
By early evening, away from the presidential palace in central Cairo, thousands of anti-Morsi protesters marched on the Nile Corniche in central Cairo, chanting, "The people want the fall of the regime."
But though the number of protesters was still growing, there was no immediate sign that the clashes were turning into a broader conflagration, like the deadly violence that broke out at the palace in December, when supporters of President Morsi fought with anti-government protesters. The Muslim Brotherhood said on its Twitter account that it was not sending its members to the protest, and that it would not "be dragged into violence."
With Egypt's political elites warring and street violence taking on a life of its own, young revolutionaries organized a rare meeting of the country's polarized political forces on Tuesday.
The meeting included the leaders of the secular-leaning opposition, and the Muslim Brotherhood, and resulted in a statement in which all the participants agreed to condemn violence. Despite those statements, many doubted whether any of the participants had the influence to alter the dynamics on the ground.
In the last few days, the violence has abated in the cities along the Suez Canal, including in Port Said, where most of the deaths occurred -- but only after the police largely disappeared from the streets, leaving the army in charge of security. In Cairo, clashes occur daily at what has become a regular spot, at the foot of the Kasr el-Nil bridge near Tahrir Square.
"The protests and the violence seem to not be in the full control of anyone, including the opposition," said Samer S. Shehata, an assistant professor of Arab politics at Georgetown University and an expert on Egyptian politics. "Things are more critical in some senses than the days when Mubarak was ousted. The authority of the state is really in question. Some people are no longer accepting the legitimacy of political institutions, including the presidency -- and not just the officeholder," he said.
Several factors would determine whether efforts at a dialogue, like the one on Thursday, could pull Egypt from the brink, he said. They could succeed, he said, if Mr. Morsi and the Brotherhood "realize the gravity of the situation, and realize, in a self-interested way, that they have lost many people who supported them previously, including many who held their noses and voted for Morsi," Mr. Shehata said, adding, "Will Morsi and the F.J.P. make serious concessions, including vesting the opposition in the process?"
Even then, he said: "Will the people on the street, who aren't following the instructions of the opposition, take the developments to heart and go home?"
Mai Ayyad contributed reporting.
This article originally appeared in The New York Times.