Five European countries have concluded that Russian opposition leader Alexei Navalny died after being poisoned with a highly toxic substance known as epibatidine, disputing Russia’s earlier claim that his death was from natural causes.

In a joint statement, the United Kingdom, France, Sweden, the Netherlands and Germany said laboratory analysis of samples linked to Navalny detected the presence of epibatidine — a potent compound associated with certain South American poison dart frogs. The governments said the toxicity of the substance, combined with reported symptoms before his death, makes poisoning the most likely cause.

“Russia claimed that Navalny died of natural causes. But given the toxicity of epibatidine and reported symptoms, poisoning was highly likely the cause of his death,” the statement said.

Navalny died in February 2024 at the age of 47 while imprisoned in a penal colony north of the Arctic Circle. Russia’s Federal Penitentiary Service announced at the time that he collapsed after a walk and could not be revived. Authorities maintained that his death was natural.

The European statement challenged that explanation, noting that Navalny died in custody.

“Navalny died while held in prison, meaning Russia had the means, motive and opportunity to administer this poison to him,” the five governments said.

U.S. Reaction

Speaking at a press conference in Bratislava alongside Slovakia’s prime minister, U.S. Secretary of State Marco Rubio addressed questions about why Washington was not part of the joint declaration.

“Look, those countries came to that conclusion. They coordinated that,” Rubio said. “Doesn't mean we disagree with the outcome. We just, it wasn't, you know, our endeavor.”

He added, “We obviously are aware of the report. It's a troubling report. We're aware of that case of Mr. Navalny, and certainly it's, you know – we don't have any reason to question it, or we're not disputing or getting into a fight with these countries over it, but it was their report, and they put that out there.”

Family Response

Navalny’s widow, Yulia Navalnaya, said she had long believed her husband was poisoned.

“I was certain from the first day that my husband had been poisoned, but now there is proof: Putin killed Alexei with chemical weapon,” she wrote in a social media post.

She thanked the countries involved in the investigation and called for accountability.

Moscow Rejects Findings

The Russian Embassy in the United Kingdom dismissed the European conclusions.

“There is no reason whatsoever to credit such ‘findings’ by Western ‘experts’,” the embassy said in a statement posted on social media.

Navalny had been one of President Vladimir Putin’s most prominent critics. In 2023, a Russian court sentenced him to 19 years in prison on extremism charges, adding to a previous sentence of nearly 12 years. Later that year, he was transferred to a “special regime” facility in the Arctic.

The latest findings deepen the dispute between Russia and several Western governments over the circumstances surrounding Navalny’s death.