As many as 200 people were killed and 600 injured after commandos stormed a school in southern Russia on Friday where armed militants held hostages for the past three days.

The number of deaths is expected to rise as debris is cleared from the school, said officials.

As night fell on the scene, Russian commanders said all of the hostage-takers had been either killed or captured and that military activities had ended. However, conflicting reports suggested four militants remained at large.

Emergency officials said they had identified 95 bodies. As many as 550 people were hospitalized – including more than 300 children. Up to 1,500 people may have been held in the school.

Russian health ministry officials said 92 of the hospitalized children are in "very grave" condition.

As many as nine of the hostage-takers were Arabs, an aide to Russian President Vladimir Putin told the Interfax news agency.

Several of the militants managed to flee from the school during the raid, hiding out in a nearby house. Russian security forces, some in civilian clothes, hunted through the streets of the town of 30,000 people, trading fire with the militants.

One hostage told the Associated Press that some of the militants, including women, wore suicide belts.

Interfax had earlier reported that the hostages were killed when the school roof collapsed. The hostage-takers were believed to have mined the building, and a reporter with British ITV News said it appeared explosives had been set off in the gymnasium.

World reaction was swift as United Nations Secretary General Kofi Annan said he was "horrified" by the loss of human life. U.S. President George W. Bush said his thoughts and prayers were with the Russian people, while Prime Minister Paul Martin issued a statement saying Canadians were outraged by such "barbaric acts of terrorism."

Explosions mark start of battle

According to a senior Russian security official, the end of the three-day siege came when the militants agreed to allow soldiers to remove the bodies of people who had been killed in the initial stages of the hostage-taking on Wednesday.

As the soldiers collected the bodies, there was an explosion from inside the school, located in the town of Beslan, near the republic of Chechnya.

Dozens of children then fled the scene, with the hostage-takers firing on them. The Russian forces returned fire and then moved in, the official said.

Some people escaping the building fainted when they reached rescuers. Many were dehydrated because the gymnasium where they were held had been so hot.

The hostage-takers had refused to let food or water into the school throughout the standoff.

A number of hostages, covered in blood, were carried away in stretchers to local hospitals or a makeshift field hospital set up several kilometres from the school. Several bodies covered in white sheets are lying on the ground near the field hospital.

Desperate family members crowded around lists of the dead and injured posted on hospital walls.

A female hostage who managed to escape told the Associated Press that gunmen threatend to shoot people if any of the children made a sound. Adults begged children to drink their own urine because their captors wouldn't give them any food or water, she said.

The senior security official said the assault on the school was not planned, and that officials were prepared to continue negotiations with the hostage-takers.

It's not clear what the militants were seeking, but reports say they wanted Russian troops to leave Chechnya and freedom for some Chechen rebels. The school is located in North Ossetia near Chechnya, where rebels have been fighting for independence from Moscow for a decade.