Hundreds of Egyptian soldiers in riot gear swept through Cairo's Tahrir Square early Monday and opened fire on protesters demanding an immediate end to military rule. The Health Ministry said at least three people were killed, bringing the death toll for four days of clashes to 14.

Violence has been raging in Cairo since Friday, when military forces guarding the Cabinet building near Tahrir Square heavily cracked down on a 3-week-old sit-in to demand Egypt's ruling generals immediately hand power to a civilian authority.

The raid early Monday may have been an attempt by the military to keep protesters away from key government buildings near the square, including parliament and the Interior Ministry, which is in charge of the hated police force.

Ahmed Saad, a field hospital doctor who witnessed the crackdown, said six people were killed by gunshots, giving a toll twice that of the Health Ministry's. He said troops stormed a mosque on the square, beating up protesters who spent the night inside.

"It was like a rain of bullets in the early morning," Saad said.

The ruling generals, who took power 10 months ago after the popular uprising that forced longtime ruler Hosni Mubarak to step down, have described the clashes as part of a "conspiracy" against Egypt.

The pro-democracy protesters have decried the military's heavy-handed crackdown. Activists have flooded social network sites and other media with photos and video of troops beating and attacking protesters.

Some widely circulated footage shows an army officer firing a pistol at protesters _ though it is not clear whether he was using live ammunition. Other images show soldiers dragging women by the hair and ferociously beating, kicking and stomping on protesters cowering on the ground.

In the middle of violence, a research center set up during France's three-year occupation of Egypt in the late 18th century caught fire and was gutted. On Monday, archive officials and dozens of volunteering protesters tried to salvage valuable books and documents from the center. The two-story building is in danger of collapsing after the roof caved in.

Inside the smoldering building, there were piles of burnt furniture, twisted metal and demolished walls. A double human chain by protesters surrounded the building to prevent any new attempts of sabotage.