UNITED NATIONS - Russia’s longtime U.N. Ambassador, Vitaly Churkin, died suddenly on Monday in New York, a day before he would have turned 65 years old.

The Russian foreign ministry announced his death in a statement, giving no details of the circumstances. The president of the U.N. General Assembly, Peter Thomson, told VOA that he was informed Churkin had “some sort of cardiac arrest” at the Russian Mission and was taken to a hospital where he died.

Former U.N. Secretary-General Ban Ki-moon, who was in office for most of Churkin's time at the U.N., called him "an outstanding diplomat and an intellectual star."

"His diplomatic skills, quick wit, and ready sense of humor will long be remembered by those who knew him and by those who will study the history of the United Nations for years to come," Ban said.

Current U.N. chief Antonio Guterres said Churkin was a "forceful presence" and a "uniquely skilled diplomat" whose insights will be missed.

Churkin's fellow U.N. diplomats immediately took to social media to express their shock and sadness at his sudden passing.

“Absolutely devastated to hear that my friend & colleague Vitaly Churkin has died,” tweeted Britain’s U.N. envoy Matthew Rycroft. “A diplomatic giant & wonderful character. RIP” he added.

“Shocked to learn of the passing of our dear colleague Vitaly Churkin,” Sweden’s U.N. Ambassador Olof Skoog wrote. “He will be deeply missed. Deepest condolences to his family.”

The new U.S. ambassador to the U.N., Nikki Haley, paid tribute to a "gracious colleague."

"We did not always see things the same way, but he unquestionably advocated his country's positions with great skill. We send our prayers and heartfelt condolences to lift up his family and to the Russian people," she said in a statement.

General Assembly President Thomson called for a minute of silence during an afternoon meeting at U.N. headquarters. In emotional remarks, he said "not only has Russia lost one of its truest sons here at the United Nations, we have lost one of our truest."

"His name shall live on in the annals of this organization's history," Thomson said.

WATCH: UN's Thomson: Churkin's Name Will Live on in UN History



Kenya's ambassador, Macharia Kamau, described Churkin as "a very calm and purposeful diplomat" and praised him for understanding the problems of smaller countries, not just big ones.

"He was a deeply experienced and able diplomat, a defender of his country, a believer in the multilateral system and the work of the United Nations, and someone who we all respected and cherished very much," UAE Ambassador Lana Nusseibeh said.

Road to diplomacy

Vitaly Ivanovich Churkin was born in Moscow on Feb. 21, 1952. As a young boy he appeared in at least three films – two were about Vladimir Lenin.



He later was a graduate of the Moscow State Institute of International Relations and went on to earn a Ph.D. in history from the USSR Diplomatic Academy.



Churkin had a distinguished career as a Russian diplomat, joining the foreign ministry in 1974. He was his government’s Special Representative to the talks on Former Yugoslavia in the early 1990s and later served as ambassador to Belgium (1994-1998) and Canada (1998-2003).



U.N. posting



In 2006, he presented his credentials to then-Secretary-General Kofi Annan and took up his post as U.N. ambassador, which he held until his death. In the more than a decade Churkin was envoy to the world body, he was widely respected by colleagues, even those whose governments had adversarial relationships with Moscow.



In the past six years, his job grew more difficult as Moscow became more isolated due to its annexation of the Crimea and its support for the regime of Syria’s Bashar al-Assad.



He often clashed in the Security Council chamber with former U.S. Ambassador Samantha Power. At a heated council meeting in December on the situation in the besieged Syrian city of Aleppo, Power called out Moscow for denying and obfuscating facts and aiding and abetting attacks on civilians. Churkin retorted that she sounded like “Mother Theresa” for scolding Moscow and urged her to “remember the track record of your country.”

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



Churkin was known as a tough negotiator and a top-notch diplomat. Many expected he would be appointed foreign minister if Sergei Lavrov retired.



Vitaly Churkin is survived by his wife, Irina, and two adult children.