Boris Bondarev, 41, said he had "never been so ashamed of my country" and the "aggressive war" waged by President Vladimir Putin's forces.

He said what his government was doing was "intolerable".

Mr Bondarev, who worked for the country's permanent mission at the United Nations in Geneva, added: "As a civil servant, I have to carry a share of responsibility for that, and I don't want to do that."

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He said he "disagreed" and "disapproved" with the current policy by Moscow and "as a Russian diplomat, (I) can no longer be associated with this".

"I went to the mission like any other Monday morning and I forwarded my resignation letter and I walked out."

He spoke of his fears, saying: "Against my safety... yes, I'm concerned about that, yeah. There is a possibility, I think so."

It is a rare political resignation over the war, which began three months ago.

Asked if any of his colleagues felt the same, Mr Bondarev said: "Not all Russian diplomats are warmongering. They are reasonable, but they have to keep their mouths shut."

Mr Bondarev, who worked as a counsellor on arms control, suggested others could be put off from also going public in the event that he is prosecuted.

"If my case is prosecuted, then if other people want to follow, they would not," he said.

Mr Putin's government has sought to crack down on dissent over the war in Ukraine and how what the Kremlin calls the "special military operation" is proceeding.

Mr Bondarev said those who decided to launch the war "want only one thing - to remain in power forever, live in pompous tasteless palaces, sail on yachts comparable in tonnage and cost to the entire Russian Navy, enjoying unlimited power and complete impunity".

He added: "Today, the ministry of foreign affairs is not about diplomacy. It is all about warmongering, lies and hatred."

The Russian envoy announced his exit on the website LinkedIn.

"I studied to be a diplomat and have been a diplomat for 20 years," he wrote.

"The [Russian foreign] ministry has become my home and family. But I simply cannot any longer share in this bloody, witless and absolutely needless ignominy."

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He also said he had no plans to leave Geneva.

He said: "[I] don't know for now what I'm going to do next. I'm thinking about it, but I think if I have to go back to Russia, then the prospects maybe not very pleasant."

The West has imposed sweeping sanctions on Russia and provided Ukraine with military support in response to the invasion.

Hiller Neuer, executive director of the advocacy group UN Watch, said: "Boris Bondarev is a hero."

A spokesman for the Russian mission did not immediately respond to calls.

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