Russian opposition leader Alexei Navalny was poisoned by the Kremlin with a lethal toxin derived from the skin of poison dart frogs, five European countries said Saturday.

The foreign ministries of the U.K., France, Germany, Sweden and the Netherlands said analysis of samples from Navalny, who died two years ago, “have conclusively confirmed the presence of epibatidine.” It is a toxin found in poison dart frogs in South America that is not found naturally in Russia, they said.

The countries said in a joint statement that “Russia had the means, motive and opportunity to administer this poison.” They said they were reporting Russia to the Organization for the Prohibition of Chemical Weapons for a breach of the Chemical Weapons Convention.