Russia's ambassador to the UN, Vitaly Churkin, has died at the age of 64, the Russian foreign ministry has confirmed.

Churkin had been Russia's permanent representative to the UN since 2006, having previously held a number of ambassadorial positions.

His death in New York, just a day ahead of his 65th birthday, was unexpected and the cause of death was not immediately known.

The diplomat fell ill in his office at Russia's UN mission and was taken to Columbia Presbyterian Hospital, according to the Associated Press, which quoted Russia's deputy UN ambassador, Vladimir Safronkov.

UN colleagues have extended their condolences to Moscow, the Tass news agency reported.

Britain's UN ambassador, Matthew Rycroft, called Churkin a "diplomatic giant" and a "wonderful character".