CAIRO -- Angry mobs of Islamists battled secular protesters with fists, rocks and gasoline bombs in the streets around the presidential palace for hours Wednesday night in the first major outbreak of violence between political factions since the revolt against then-President Hosni Mubarak began nearly two years ago.
Three senior advisers to Mubarak's successor, Mohammed Morsi, Egypt's first elected president, resigned during the clashes, blaming him for the bloodshed, and his prime minister implored both sides to pull back in order to make room for "dialogue."
The scale of the clashes, in an affluent neighborhood just outside Mr. Morsi's office in the presidential palace, raised the first doubts about Mr. Morsi's attempt to hold a referendum Dec. 15 to approve a draft constitution approved by his Islamist allies over the objections of his secular opposition and the Coptic Christian church.
Periodic gunshot blasts could be heard at the front lines of the fight, and secular protesters displayed birdshot wounds and pellets. But it could not be determined whether riot police or Islamists or the opposition had fired the guns.
Many in both camps brandished makeshift clubs, and on the secular side a few carried machetes. By 11 p.m., more than 211 people had been injured, the health ministry said. Each side claimed that one of its own had been killed, spurring on the battle, although the authorities had not confirmed either death. By then, thousands had joined the battle on each side.
Riot police tried to fight off or break up the crowds with tear gas, but by about 9:30 p.m. the security forces had all but withdrawn. They continued to try to separate the two sides across one boulevard but stayed out of the battle that raged on all around.
In a city square on the Islamist side of the battle lines, a loudspeaker on the top of a moving car blared out exhortations that the fight was about more than politics or Mr. Morsi.
"This is not a fight for an individual, this is not a fight for President Morsi," the speaker declared. "We are fighting for God's law, against the secularists and liberals."
Protesters reportedly set fire to Muslim Brotherhood political offices in the cities of Suez and Ismailia.
Even after two years of periodic battles between protesters and police, Egyptians said they were shocked and alarmed by the spectacle of fellow citizens drawing blood over matters of ideology or political power.
Distrust and animosity between Islamists and their secular opponents have mired the outcome of Egypt's promised transition to democracy in debates about the legitimacy of the new government and its new leaders' commitment to the rule of law.
The clashes followed two weeks of sporadic violence around the country since Mr. Morsi, a former leader of the Muslim Brotherhood movement, seized temporary powers beyond the review of any court, removing the last check on his authority until ratification of the new constitution.
Mr. Morsi has said he needed the expanded powers to block a conspiracy by corrupt businessmen, Mubarak-appointed judges and opposition leaders to thwart Egypt's transition to a constitutional democracy.
His secular critics have accused Mr. Morsi and the Islamists of seeking to establish a new dictatorship, in part by ramming through a rushed constitution that they charge could ultimately give new power over society to Muslim scholars and Islamists groups. And each side's actions have confirmed the other's fears.
As Wednesday's clashes began, Vice President Mahmoud Mekke offered a compromise that seemed to go nowhere. Mr. Mekke proposed amending the text of the draft constitution to build more support for it before the Dec. 15 vote.
"All the political forces objecting to some articles in the constitution are welcome to provide suggestions or concepts about the articles," he said, suggesting that through "calm dialogue" both sides could agree on amendments that would be approved by the future Parliament.
The vice president, however, did not suggest any means to overcome the lack of trust in the Islamist leaders among the secular opposition, or how to persuade liberals to back down from their vow not to negotiate until Mr. Morsi relinquishes the temporary expansion of his powers and cancels the referendum.
Mohamed ElBaradei, the former United Nations diplomat, was chosen Wednesday as coordinator for the newly unified secular opposition. He urged Mr. Morsi and his allies to "see what is happening in the Egyptian street, the division, the polarization. This is something that leads us to violence and worse."
Morsi did not respond to the clashes. His party, founded by the Muslim Brotherhood, said it held Mr. ElBaradei and other secular leaders responsible for any violence.
The Brotherhood issued its own statement defending the need for Mr. Morsi's actions to fight off "treacherous plots" against Egypt's nascent democracy. It called any attempt to stop the referendum a "stumbling block."