Vitaly Churkin, who served as Russia’s permanent representative to the United Nations since 2006, “died suddenly” in New York, the Russian Foreign Ministry announced.

Churkin would have turned 65 on Tuesday.

The announcement “of the untimely passing away of Ambassador Vitaly Churkin this morning” was met with shock when it was delivered during a session at the UN headquarters.

He was a dear colleague of all of us, a deeply committed diplomat of his country and one of the finest people we have known,” a UN official who delivered the news to her colleagues said.

The moment of silence in Churkin’s memory was announced at the UN.

President Putin has expressed his condolences to Churkin’s family and to all Russian diplomats.

He was an outstanding person. He was brilliant, bright, a great diplomat of our age,” Russian Foreign Ministry spokeswoman Maria Zakharova told RT, adding that the news of Churkin’s death was “completely shocking.”

Churkin fell ill in his office at Russia’s UN mission and was taken to Columbia Presbyterian Hospital, where he died Monday, AP reported, citing Russia’s deputy UN ambassador, Vladimir Safronkov. The cause of death wasn’t immediately known, the agency reported.

He has been such a regular presence here that I am actually quite stunned. Our thoughts go to his family, to his friends and to his government,” Farhan Haq, deputy spokesman for the UN secretary-general’s office said, as quoted by Reuters.

Churkin’s former colleague, the former US ambassador to the UN, Samantha Power, wrote on Twitter she was “devastated” by the news, calling Churkin a “diplomatic maestro [and] deeply caring man who did all he [could] to bridge” the differences between the two powerful nations.

He was a strong-willed, resolute, and dutiful person, who was admired by his colleagues and envied by his enemies,” Russian Deputy Foreign Minister Sergey Ryabkov told RT.

Russia’s UN Ambassador spared no effort and devoted his life and strength “to the fight for a brighter future for this world,” Ryabkov said, adding that Churkin’s death is “a great loss not only for diplomacy, but for the country in general.

The profession of a diplomat “has become much more hectic than it used to be in the past,” Churkin said earlier this month in an interview with RT, which was one of his last. “It is stressful,” he said.

Unfortunately, the world has not become more stable than it used to be,” Churkin told RT’s Aleksey Yaroshevsky.

Before he was appointed to represent Russia at the UN in May 2006, the diplomat served as ambassador to Belgium, ambassador to Canada, and liaison ambassador to NATO and the Western European Union (WEU).

In the 2000s he was ambassador at large at Russia’s Foreign Ministry, while in the early 1990s he served as the special representative of the Russian president to the talks on the former Yugoslavia.

RT