Reporting from Cairo — Anti-government protesters kept a grim grip on the square at the center of efforts to oust Egypt's president at dawn Thursday, after a day of battles marked by horse- and camelback charges, rhythmic banging of makeshift shields and the glow of firebombs hurled in the dark.
But their continued presence in Tahrir Square came at a cost: Egypt's minister of health was quoted by Nile TV as saying four people were killed and 200 were wounded within an hour after heavy gunfire broke out just before calls to prayer echoed across the city, signifying the coming daylight.
There was no independent confirmation of the casualties or who was behind the shooting, which sounded like automatic weapons fire.
President Hosni Mubarak's supporters had converged on the square to confront the opposition Wednesday, a day after he declared he would not seek reelection this fall.
Egyptian officials had appealed for an end to the protests, saying a political dialogue couldn't begin until normal life returned to the streets.
But opponents of the 82-year-old president, who has been in power for three decades, accused his backers of orchestrating Wednesday's pitched battles.
Egyptian officials said at least three people were also killed in that fighting, with more than 600 injured.
The army, positioned around the plaza, fired into the air but did little else to intervene. The crowd of anti-government protesters, sparse compared with the hundreds of thousands in the square Tuesday, was besieged on all sides by a large force and attacked with firebombs from rooftops.
The anti-government demonstrators banged on metal shields apparently torn from a construction site, and the two sides cheered as they charged each other's lines.
The anti-Mubarak protesters organized themselves into teams. One shift manned barricades next to the Egyptian Museum, another passed stones to them to repel the pro-Mubarak forces.
An impromptu medical clinic was set up at a mosque, with several anti-government doctors treating the wounded.
The number of Mubarak supporters dissipated rapidly as dawn approached; they had been pushed back from one of the main areas where the two sides faced off.
The military had called for an end to the protests, an announcement widely seen as a signal that it had not abandoned Mubarak.
"You are the ones capable of returning normal life to Egypt," military spokesman Ismail Etman said on state television. "Your message has arrived; your demands have become known."
Omar Suleiman, a former intelligence chief appointed vice president last week, said the government could not begin talks with the opposition until normal life resumed.
The opposition said the violence Wednesday showed that any such discussions were pointless until Mubarak was gone.
"By doing this, Mubarak has cut off all channels of connections with the opposition, and we will not be carrying out any talks before Mubarak steps down," said Ayman Nour, a university professor who is a leader of the movement for greater democracy in Egypt.
The outlawed Muslim Brotherhood called on protesters to keep up the pressure on Mubarak.
"The majority of the pro-Mubarak protesters are thugs … paid and backed by the regime," said George Ishak, a longtime opposition figure. "Those burning Egypt right now are not anti-Mubarak demonstrators. They have been in the square for days and nothing like this has happened."
In Washington, White House Press Secretary Robert Gibbs said Mubarak had a chance to show the world "exactly who he is" by reforming his authoritarian government. "If any of the violence is instigated by the government, it should stop immediately," Gibbs said.
In a Twitter message sent late Wednesday, the State Department urged U.S. citizens who wanted to leave Egypt aboard a chartered flight to report to the Cairo airport immediately. "Further delay is not advisable," the Bureau of Consular Affairs said.
For Egyptians seeking change, hope turned to bitterness.
"I wanted to remove my president," whispered a furious Ramia Nalah, a 40-year-old woman with a cast on her arm, as she watched the pro-government force push toward the square Wednesday. "Now I will become a terrorist."
But Mubarak supporters spoke of his feats as a pilot in the 1973 war with Israel and said he represented stability.
Less than 24 hours earlier, Mubarak had announced that he would not seek reelection in September.
Although he called for "constitutional reform," he did not say what kind, and the "reforms" were to be led by pro-government legislators chosen in elections widely seen as fraudulent.
Anti-government demonstrators dismissed the announcement as an empty gesture.
Hazem Hosny, a professor of economics and political science at Cairo University, said the outbreak of violence was predictable, as neither side felt it could back down.
Among the anti-Mubarak forces, he said, "there is a deep feeling that a half-revolution is a grave."