Western powers have vowed to back Russia in the fight against extremists as they condemn a suicide attack on the Moscow metro that killed 38 people during the morning rush hour.
Russian Prime Minister Vladimir Putin vowed those behind the attacks would be "destroyed", as the head of Russia's FSB security service said they appeared linked to militant groups in the insurgency-wracked Northern Caucasus.
The country's key European partners Germany, France and Britain rallied to its side after the apparently coordinated strikes on two trains near the ex-KGB headquarters and Gorky Park on Monday, the deadliest attacks in Moscow in half a decade.
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And US President Barack Obamacalled his Russian counterpart Dmitry Medvedev, offering condolences and to help "bring to justice" those who planned and carried out the bombings.
German Chancellor Angela Merkel expressed her "shock and horror", as she offered her sympathies to the victims in a message to Russian President Dmitry Medvedev, her spokesman said.
World leaders 'appalled'
French President Nicolas Sarkozy said the bombings were no different from the 9/11 attacks on the United States, and Russia deserved the support of all democracies.
"Do you think there's a fundamental difference between the lunatics who blew up innocent victims in the Moscow metro and the insane people who flew planes into the Twin Towers of New York?" Sarkozy said during a meeting with Columbia University students during a trip to New York.
"When New York was attacked, all the world's democracies were attacked. And when Moscow is attacked, we are all attacked," he added.
British Prime Minister Gordon Brown said he was "appalled" at the bombing that struck at the height of the morning rush hour.
"There will never be any justification for acts such as these," Brown's spokesman told journalists, saying he had sent a message of condolence and support to the Russian president.
Bombings 'outrageous acts'
US President Barack Obama condemned the attacks as "outrageous acts", offering his "deepest condolences" to the people of Russia after "the terrible loss of life and injuries".
"The American people stand united with the people of Russia in opposition to violent extremism and heinous terrorist attacks that demonstrate such disregard for human life, and we condemn these outrageous acts," he said.
NATO Secretary-General Anders Fogh Rasmussen, who argued this weekend for the West to embrace Russia as a partner for global security, strongly condemned the Moscow attacks.
"NATO remains committed to cooperating with Russia in the fight against international terrorism," he added.
European Union president Herman Van Rompuy also sent Medvedev a message of solidarity and condolences on behalf of the 27-member EU, as did Spain, which holds the bloc's rotating presidency.
Counter-terrorism pledge
European Commission chief Jose Manuel Barroso said the EU "stands resolutely together with the Russian authorities in the efforts to counter terrorism in all its forms".
Israeli Foreign Minister Avigdor Lieberman, an immigrant from the former Soviet Union, sent his Russian counterpart condolences and said no country was safe from extremist attacks.
Chinese President Hu Jintao "strongly condemned the terrorist attacks and supported Russian efforts to strike down terrorism" in a telegram sent to Medvedev, the state-run Xinhua news agency said.
International police agency Interpol extended its help to Russia to track down the plotters behind what executive director Jean-Michel Louboutin branded as "despicable and senseless attacks".
Russia's arch-foe Georgia condemned the attacks and Georgian Foreign Minister Grigol Vashadze expressed condolences during a joint press conference in Tbilisi with Lithuanian counterpart Audronius Azubalis.
