MOSCOW - The militants who raided a school in southern Russia last week were led by a man dubbed the Colonel, who enforced obedience by killing three fellow attackers - two by detonating the explosives they had strapped to their bodies.

Two days later, the attackers were moving the explosives they rigged around the gym where hundreds of hostages were held, and a bomb went off accidentally. That began the spiral of panic that led to the bloody conclusion of the standoff, in which more than 320 people were killed.

Those details were among several disclosed by Prosecutor-General Vladimir Ustinov today in the government's first formal attempt to account for the tragedy last week. It came as Russia offered more than $10 million for information that helps "neutralize" two well-known rebel leaders from breakaway Chechnya accused of planning the attack.

Ustinov, who met with President Vladimir Putin, said 326 hostages had been killed and 727 wounded in the attack, which ended Friday in a wave of explosions and gunfire as hostages tried to flee, and special forces and armed civilians tried to help them. He said 210 of the bodies had been identified, and forensic workers were also trying to identify 32 body fragments. The death toll could rise, Ustinov said.

Various officials had previously leaked some details of the investigation, but the government had not set out its own version of events until now.

The approximately 30 attackers, including two women, had gathered in a forest early on the morning of Sept. 1 and arrived at School No. 1 in Beslan in a military-type truck and two jeeps, packed with weapons and ammunition, Ustinov said.

They herded people who had gathered to mark the first day of school to the gym. Some of the militants objected to seizing a school, and their leader, who went by the name Colonel, shot one of them. He said he would do the same to any other militants or hostages who did not show "unconditional obedience."

Later that day, he detonated the explosives worn by two female attackers, killing them, to enforce the lesson, Ustinov said.

One of the militants was stationed with his foot on a button that would set off the explosives, Ustinov said; if he lifted his foot, the bombs strung up around the school gymnasium would detonate, he said.

On Friday, the militants decided for unknown reasons to reposition the explosives, and apparently set off one bomb by mistake, Ustinov said. That sparked panic, as hostages tried to flee, and the attackers opened fire.

That led Russian forces to storm the building.

Ustinov said his information was based on interviews with witnesses and the one alleged attacker who has been confirmed detained, identified as Nur-Pashi Kulayev. Officials believe the attack in the city of Beslan was orchestrated by militants from breakaway Chechnya.

Ustinov's deputy, Sergei Fridinsky, said the bodies of 12 of the attackers had been identified.

Some 1,200 hostages had been taken at the school, Ustinov said.

On Tuesday, Russians got a horrifying glimpse of the drama from video footage filmed by the militants who captured the school. The images, aired on a Russian television station, showed the heavily armed, hooded assailants amid the crowd of women, children and men.

Hundreds of hostages were shown seated in the school's cramped gym. Many of them had their hands behind their heads. A thick streak of blood stained the wood floor.

Football-sized bundles of explosives were attached to wires and strings hanging from a basketball hoop. One attacker in camouflage and a black hood stood amid the hostages with a boot on what NTV said was a book rigged with a detonator.