Soldiers opened fire Friday on thousands of protesters defying a government ban and streaming toward the landmark square that had been the symbolic center of the uprising to break the political grip of the Gulf nation's leaders.

Officials at the main Salmaniya hospital said at least 50 people were injured, some with gunshot wounds. Some doctors and medics on emergency medical teams were in tears as they tended to the wounded. X-rays showed bullets still lodged inside victims.

"This is a war," said Dr. Bassem Deif, an orthopedic surgeon examining people with bullet-shattered bones.

Health ministry officials said in a statement that seven people were critically injured.

Protesters described a chaotic scene of tear gas clouds, bullets coming from many directions and people slipping in pools of blood as they sought cover. Some claimed the gunfire came from either helicopters or sniper nests, a day after riot police swept through the protest encampment in Pearl Square, killing at least five people and razing the tents and makeshift shelters that were inspired by the demonstrators in Cairo's Tahrir Square.

An Associated Press cameraman saw army units shooting anti-aircraft weapons, fitted on top of armored personnel carriers, above the protesters, in apparent warning shots and attempts to drive them back from security cordons about 200 yards (200 meters) from the square.

Then the soldiers turned firearms on the crowd, one marcher said.

"People started running in all directions and bullets were flying," said Ali al-Haji, a 27-year-old bank clerk. "I saw people getting shot in the legs, chest, and one man was bleeding from his head."