The United States said nothing could justify such a "terrorist act."

"We reiterate our condemnation of those who engage in terrorism," deputy State Department spokesman Adem Ereli told reporters. "No cause, no circumstances justify such actions."

In Brussels, the president of the European Commission, Romano Prodi, said the EU executive rejected any form of terrorism, "whatever the motives and whoever the authors".

Speaking for the British government, Junior Foreign Office Minister Bill Rammell said: "I condemn this vicious attack and extend my sympathies to the families."

He added that Prime Minister Tony Blair had personally sent condolences to the Russian government.

Despite European criticim of Russia's policies in Chechnya, from where the bombers were reported to have come, there was no stinting of the condemnation of the violence.

"No cause justifies the recourse to such acts," said the spokeswoman for the French foreign ministry, Cecile Pozzo di Borgo, said.

French President Jacques Chirac, who was on a visit to Tunisia, said he had "learnt with dismay about the terrible attack carried out in a suburban train that caused the death of so many people."

He said he was "indignant and deeply saddened at this terrorist act".

Chancellor Gerhard Schroeder of Germany, in a personal letter to Russian President Vladimir Putin, said he was shocked to learn of the "cruel attack".

"This hateful attack should be condemned in the strongest terms," he said.

German Foreign Minister Joschka Fischer said the bombing was a "despicable act of terror" that "fills us with dismay and outrage".

Belgian Foreign Minister Louis Michel said the attack was aimed at destabilizing Russia two days before legislative elections.

"This new despicable terrorist act against innocent civilians in Russia fills me with horror," he said in a statement.

"Those who aim to destabilize the southern part of Russia bear a particularly heavy responsibility. On the eve of the December 7 elections, Russia must be able to choose its future serenely and freely," Michel added.

Prodi also said the blast was aimed at destabilizing the election. He said the European Commission was committed to the fight against world terrorism "side by side with Russia and other international partners, in full respect for the rules of law".