Russian Deputy Prosecutor-General Sergei Fridinskii announced that 322 people are confirmed dead, 155 of them children, with the number of dead likely to grow, although "probably not by much."
Fridinskii said 26 militants were involved in the hostage taking, holding some 1,000 children, parents, and teachers in the school's sports hall for two days without food or water.
Fridinskii said all of the hostage takers were believed killed. Some were reported to be of Arab origin.
As the death toll climbed as more bodies were discovered at the scene, President Vladimir Putin paid a brief visit to Beslan this morning, saying all of Russia shares the town's grief.
He also said no one had planned to use force to end the siege: "Of course we examined all possible courses of action, but use of force was not planned. Events developed very quickly and unexpectedly. The special forces showed courage."
Putin addressed the public in a televised address later in the day, declaring 6 and 7 September days of national mourning in Russia and signaling that the bloodshed requires a stepped up effort by the country's security forces.
Putin suggested imminent changes in the way security is maintained in southern Russia in particular. "In the near future there will be prepared a range of measures designed to strengthen the unity of the country. Second, I consider it necessary to create a new system to better coordinate forces and means for maintaining control in the North Caucasus," he said.
"We are dealing with a direct intervention of international terror against Russia, with a total, cruel, and all-powerful war that again and again takes the lives of our fellow countrymen," Putin said, according to Reuters. "We must create a much more effective system of security. We must demand that our security forces act at a level appropriate to the level and scope of the new threats."
Authorities say they were forced to storm the school on 3 September when the gunmen opened fire on fleeing children.
But the assault quickly devolved into nightmarish scenes of horror.
Screaming, bloodied, and half-naked children fled the school or wailed in the arms of running soldiers, as automatic weapons fire burst around them.
The loss of life in Russia drew sympathy from around the world.
But there were also questions about the tactics used by special forces. The European Union said in a statement it wants an explanation from Russia "how this tragedy could have happened."
That drew an angry reaction today from Russian Foreign Minister Sergei Lavrov, who called the criticism and its timing "sacrilegious."
(from news agency and RFE/RL reports)
[For more on the North Ossetian hostage tragedy and the recent wave of terrorism in Russia, see RFE/RL's "Terror in Russia"