Hundreds of Egyptian soldiers in riot gear swept through Cairo's Tahrir Square today firing 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 troops guarding the cabinet building near Tahrir Square heavily cracked down on a three-week-old sit-in to demand Egypt's ruling generals immediately hand power to a civilian authority.

The latest raid 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 doctor who witnessed it, 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," he said.

The ruling generals, who took power 10 months ago after the popular uprising that forced long-time 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 stamping on protesters cowering on the ground.