Updated

The Egyptian military is showing its force Thursday morning in Tahrir Square, firing shots into the air over protesters trying to topple Hosni Mubarak’s 30-year rule.

The increased violence comes as the United States Department announces it would prefer elections now slated for September be moved up. State Department spokesman P.J. Crowley said the sooner Egypt holds free and fair elections, the better.

The State Department also advised U.S. citizens remaining in Egypt to leave immediately as violence spread.

The military is attempting to clear out protesters from Tahrir Square after thousands of anti-government demonstrators and pro-Mubarak supporters clashed in the streets, hurling Molotov cocktails and rocks at each other. Gunman were seen firing into the square's crowd early Thursday morning.

Three soldiers were killed and at least 600 were injured from the violent protests, according to Egypt's state TV. A fourth person was killed early Thursday according to reports from Reuters and Al Jazeera.

More On This...

The protesters accused Mubarak's regime of unleashing a force of paid thugs and plainclothes police to crush their unprecedented 9-day-old movement, a day after the 82-year-old president refused to step down. They showed off police ID badges they said were wrested from their attackers. Some government workers said their employers ordered them into the streets.

Eyewitnesses say people have taken to the rooftops of buildings, throwing tear gas bombs onto Tahrir Square. A portion of the famed Egyptian Museum in Cairo was reportedly set on fire earlier Wednesday from one of the Molotov cocktails, according to Al Arabiya.

The notion that the state may have coordinated violence against protesters, who had kept a peaceful vigil in Tahrir Square for five days, prompted a sharp rebuke from the Obama administration.

"If any of the violence is instigated by the government, it should stop immediately," said White House Press Secretary Robert Gibbs.

The violence marked a dangerous new phase in Egypt's upheaval -- the first significant violence between supporters of the two camps in more than a week of anti-government protests. Clashes erupted after Mubarak spoke on national TV Tuesday evening, rejecting demands he step down immediately and saying he would serve out the remaining seven months of his term until September elections.

Protesters, who initially took to the streets on Jan. 25 after years of tight state control, are rejecting Mubarak’s speech as too little too late and renewing their demands he leave immediately.

A military spokesman appeared on Egypt's state TV Wednesday and asked protesters to disperse so life in Egypt could return to normal. The announcement could mark a major turn in the attitude of the army, which for the past two days has allowed protests to swell, reaching their largest size yet on Tuesday when a quarter-million people peacefully packed into Tahrir Square.

Mubarak’s regime began to rally supporters in significant numbers for the first time Wednesday. Around 3,000 supporters broke through a human chain of protesters trying to defend the thousands gathered in Tahrir, according to an Associated Press reporter at the scene. At one point, a small contingent of pro-Mubarak forces on horseback and camels rushed into the anti-Mubarak crowds, swinging whips and sticks to beat people.

After midnight, 10 hours after the clashes began, the two sides were locked in a standoff at a street corner, with the anti-Mubarak protesters hunkered behind a line of metal sheets hurling firebombs back and forth with government backers on the rooftop above. The rain of bottles of flaming gasoline set nearby cars and wreckage on the sidewalk ablaze.

The scenes of mayhem were certain to add to the fear that is already running high in this capital of 18 million people after a weekend of looting and lawlessness and the escape of thousands of prisoners from jails in the chaos.

Soldiers surrounding Tahrir Square fired occasional shots in the air throughout the day but did not appear to otherwise intervene in the fierce clashes and no uniformed police were seen. Most of the troops took shelter behind or inside the armored vehicles and tanks stationed at the entrances to the square.

"Why don't you protect us?" some protesters shouted at the soldiers, who replied they did not have orders to do so and told people to go home.

"The army is neglectful. They let them in," said Emad Nafa, a 52-year-old among the protesters, who for days had showered the military with affection for its neutral stance.

The movement against Mubarak resists any sentiment that Mubarak’s concession may have been enough. Protesters have vowed to intensify demonstrations to force Mubarak out by Friday.

"We recognize deceit when we see it," said protester Nasser Saad Abdel-Latif. "No one will lose their energy ... We won't go until he goes."

Wednesday's events suggest the regime aims to put an end to the unrest to let Mubarak shape the transition as he chooses over the next months. Mubarak has offered negotiations with protest leaders over democratic reforms, but they have refused any talks until he steps down.

As if to show the public the crisis was ending, the government began to reinstate Internet service after days of an unprecedented cutoff. State TV announced the easing of a nighttime curfew, which now runs from 5 p.m. to 7 a.m. instead of 3 p.m. to 8 a.m.

The Associated Press contributed to this report.