Five European countries — including Britain, France and Germany — accused Russia of “poisoning” opposition leader Alexei Navalny in prison in 2024 using a “rare toxin”, on Saturday on the sidelines of the Munich Security Conference.

“The UK, Sweden, France, Germany and The Netherlands are confident that Alexei Navalny was poisoned with a lethal toxin,” the countries said in a joint statement, following “analyses of samples” from his body.

The staunch critic of Russian President Vladimir Putin died in an Arctic prison in February 2024, while serving a 19-year prison sentence.

The epibatidine toxin found in the skin of dart frogs native to South America was found in samples and “highly likely resulted in his death”, the European states said.

“Only the Russian state had the means, motive and opportunity to deploy this lethal toxin to target Navalny during his imprisonment in a Russian penal colony in Siberia, and we hold it responsible for his death,” the UK foreign office added in a statement.

Navalny’s widow, Yulia Navalnya, said it was now “science-proven” that the Kremlin opponent had been murdered.

“Two years ago I came on stage here and said that it was Vladimir Putin who killed my husband,” Navalnaya said on the sidelines of the conference.

“I was of course certain that it was a murder … but back then it was just words. But today these words have become science-proven facts,” Navalnaya added.

Navalnaya last September said that laboratory analysis of smuggled biological samples found he was killed by poisoning.

“Today, beside his widow, the UK is shining a light on the Kremlin’s barbaric plot to silence his voice,” UK Foreign Secretary Yvette Cooper, who met Navalnaya while attending the Munich conference, said in a statement.

The countries said they had reported Russia to the world’s chemical weapons watchdog — the Organisation for the Prohibition of Chemical Weapons — over the finding.

“We are further concerned that Russia did not destroy all of its chemical weapons,” the countries said, accusing Moscow of breaching the Chemical Weapons Convention.

Navalny was previously poisoned with the Soviet-era nerve agent Novichok in 2020 while campaigning in Siberia and was flown to Germany on an emergency evacuation flight, where he spent months recovering.

The charismatic anti-corruption campaigner had rallied hundreds of thousands across Russia in anti-Kremlin protests as he exposed the alleged ill-gotten gains of Putin’s inner circle.