Russian opposition leader Alexei Navalny was killed using a deadly toxin found in poison dart frogs in South America, the UK and some of its European allies have said.
Traces of epibatidine were found in samples from Navalny's body and highly likely resulted in his death in a Siberian penal colony two years ago, the UK Foreign Office said.
The allies said only the Russian state had the "means, motive and opportunity" to deploy this lethal toxin.
The Kremlin dismissed the finding as "an information campaign", according to Tass news agency.
Epibatidine is a natural neurotoxin isolated from the skin of the Ecuadorian poison dart frog, according to toxicology expert Jill Johnson.
