Moscow: Russia 's combative ambassador to the United Nations, Vitaly Churkin , died suddenly in New York on Monday after being taken ill at work, the Russian Foreign Ministry said.

The ministry gave no details on the circumstances of his death but offered condolences to his relatives and said the diplomat had died one day before his 65th birthday. It declined to comment on reports that Churkin had been taken to a hospital shortly before his death.

A US government official, who was not authorized to speak publicly on the case, said that Churkin had died of an apparent heart attack. A federal law enforcement official, also speaking on condition of anonymity, said that there appeared to be nothing unusual about the ambassador's death.

The New York Post quoted unnamed sources as saying Churkin had been rushed to a Manhattan hospital from the Russian embassy after falling ill with a cardiac condition. President Vladimir Putin was deeply upset by the news and had greatly valued Churkin 's professionalism and diplomatic talent, Russian news agencies quoted the Kremlin as saying. Tass news agency quoted Churkin 's deputy, Pyotr Ilyichev, as saying: "The loss sustained by Russia is grave and irreplaceable.

"Ambassador Churkin remained at his work post until the last minute. He devoted his whole life to defending the interests of Russia and was to be found on the very front lines and in the most stressful posts." Churkin was a pugnacious defender of Russian policy, notably its intensive bombing of the Syrian city of Aleppo last year to crush rebels opposed to President Bashar al-Assad.