Update: according to Reuters, Vladimir Putin was deeply upset to learn of the death of Vitaly Churkin, Russian news agencies cited Kremlin spokesman Dmitry Peskov as saying on Monday.

"The head of state highly valued Churkin's professionalism and diplomatic talent," Peskov said.

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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 died one day before his 65th birthday. Russia's deputy U.N. ambassador, Vladimir Safronkov, told AP that Churkin became ill and was taken to Columbia Presbyterian Hospital, where he died Monday.

Churkin was at the Russian embassy on East 67th Street when he became sick with a “cardiac condition” around 9:30 am, sources told the New York Post. A Russian Embassy spokesperson told CBS News that they believe Churkin died of a heart attack but they do not yet have official word on the cause of death.

As the AP adds, Churkin has been Russia's envoy at the United Nations for a little over a decade and was considered Moscow's great champion at the U.N. He had a reputation for an acute wit and sharp repartee especially with his American and Western counterparts. He was previously ambassador at large and earlier served as the foreign ministry spokesman.



Colleagues took to social media to react to Churkin’s death, starting with Churkin's old nemesis Samantha Power:

Devastated by passing of Russian UN Amb Vitaly Churkin.Diplomatic maestro &deeply caring man who did all he cld to bridge US-RUS differences — Samantha Power (@SamanthaJPower) February 20, 2017

Absolutely devastated to hear that my friend & colleague Vitaly Churkin has died. A diplomatic giant & wonderful character. RIP — Matthew Rycroft (@MatthewRycroft1) February 20, 2017

Saddened to hear news of a colleague Amb Vitaly Churkin of Russian Federation suddenly passing away. Our condolences to his family & country — Maleeha Lodhi (@LodhiMaleeha) February 20, 2017

Our sincere condolences on the passing away of Permanent Representative Vitaly Churkin. We are saddened by the news of your loss @RussiaUN — Juan Carlos Mendoza (@jcmendozagarcia) February 20, 2017

The announcement "of Churkin's passing 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.

Shocking news to hear the passing away of Amb Vitaly Churkin. A brilliant ambassador who served his country & people. May he rest in peace. pic.twitter.com/pFodXqs5Qm — @kamaNY (@kamapradipta) February 20, 2017

The Russian foreign 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. Here is the statement issued moments ago from the Russian Foreign Ministry:

A prominent Russian diplomat has passed away while at work. We'd like to express our sincere condolences to Vitaly Churkin's family. The Russian Foreign Ministry deeply regrets to announce that Russia’s Permanent Representative to the United Nations Vitaly Ivanovich Churkin has died suddenly in New York on February 20, a day ahead of his 65th birthday.

"He was an outstanding person. He was brilliant, bright, a great diplomat of our age," Russian Foreign Ministry spokeswoman Maria Zakharova said, adding that the news of Churkin's death was "completely shocking."

Interviewed Churkin just 2 weeks ago. He looked in good health and was very energetic during the interview. Shockedhttps://t.co/SAcWVZ1wEJ — Alexey Yaroshevsky (@Yaro_RT) February 20, 2017

According to Sputnik, Russia's Deputy Permanent Representative to the United Nations Yevgeniy Zagaynov said about Churkin that he kept working "till the very end." The representative of the UN Secretary-General said that the UN was shocked by the news, extending their condolences to Moscow.

Perhaps the best known Russian diplomat alongside Sergey Lavrov, Vitaly Ivanovich Churkin was born in Moscow in 1952. He graduated from the Moscow State Institute of International Relations in 1974, beginning his decades-long career at the Ministry of Foreign Affairs shortly.

Ambassador Churkin, who held a Ph.D in history, served as Russia's Permanent Representative to the United Nations since 2006, where he has clashed on numerous occasions with opposing members of the Security Council whose decisions Russia has vetoed more than once. Prior to this appointment, he was Ambassador at Large at the Ministry of Foreign Affairs of the Russian Federation (2003-2006), Ambassador to Canada (1998-2003), Ambassador to Belgium and Liaison Ambassador to NATO and WEU (1994-1998), Deputy Foreign Minister and Special Representative of the President of the Russian Federation to the talks on Former Yugoslavia (1992-1994), Director of the Information Department of the Ministry of Foreign Affairs of the USSR/Russian Federation (1990-1992).

Churkin is survived by his wife and two children.