Reaction: Tragic, despicable, inhumane, cowardly, barbaric, evil and astonishing - the deaths of a hundred or more people including children in a siege in Russia sparked strong words for the hostage-takers from world leaders.
"The responsibility for the tragic loss of life rests with the terrorists," said White House spokesman Scott McClellan.
"The United States stands side by side with Russia in our global fight against terrorism," he said. "There is no justification for the taking of innocent life, and the barbaric nature of this terrorist act is despicable.
"Our thoughts are with the Russian people during this difficult time. We extend our deepest condolences to the families of the victims."
Some analysts questioned Russian security forces' tactics in storming the school, though Moscow has said the move was forced on them when hostage-takers opened fire on fleeing children.
"I suspect that [Russian President Vladimir\] Putin's immediate concern will have been to be seen to be strong rather than be seen to be negotiating," said Alex Standish, editor of Jane's Intelligence Digest.
"And if that means sacrificing civilians caught up in the middle, I don't suspect that is the key issue as far as Putin is concerned," he said.
But world leaders focused on support and solidarity for Russia.
Chief Vatican spokesman Joaquin Navarro-Valls said news of the tragedy was received with sadness at the Vatican.
"There is sadness for the huge loss of life and for the immense pain of the parents and families of victims resulting from an act of terrorism," he said.
German Chancellor Gerhard Schröder said everyone in his country was "moved with sympathy" for the victims and their families.
"Here terrorists without conscience tried to reach political goals by murdering people," he said.
Gernot Erler, foreign policy expert of Schröder's Social Democrats, said Putin could not have given in to the hostage takers.
"In this case he really had no choice but to say No to the demands," Mr Erler told NDR radio.
Egypt expressed its sympathy for the "friendly Russian people in this ordeal", while Israel's foreign minister called the events an "an intolerable criminal terror act".
Dutch Foreign Minister Bernard Bot, whose country holds the rotating EU presidency, said it was a "deep human tragedy".
"This shows once again that we have to do everything in our power to combat terrorism," he said.
"We have to unconditionally condemn terrorism in whatever form it presents itself. Let it also be a stimulus for us to work more closely together in this field to avoid similar tragedies."
Italian Prime Minister Silvio Berlusconi said the world was holding its breath as the siege unfolded. "These are astonishing times, the level of insecurity is very high," he said.
The fact that so many of the victims were children provoked universal condemnation.
"Terrorism has shown one of its ugliest faces - attacking children," said Polish Defence Minister Jerzy Szmajdzinski.
Greece condemned what it called a "cowardly terrorist action". Spain said there was a "wave of concern" for the victims.
Danish Foreign Minister Per Stig Moeller said it was "totally inhumane" to take children as hostages.
"There is no excuse for that and it harms any kind of sympathy for the Chechen cause," he said.