The UK wants action taken following evidence Russia killed political prisoner Alexei Navalny with frog poison, Foreign Secretary Yvette Cooper said.
Two years ago, Russian opposition leader Navalny, a vocal critic of President Vladimir Putin, died suddenly in the the Siberian prison where he was being held on trumped-up charges.
European labs have now confirmed he died from the obscure poison, which Cooper says only the Russian government had the "means, motive and opportunity" to use.
She told the BBC proof of the toxin was a "clear breach" of international chemical weapons rules and "we do want to see action" taken, which could include continuing coordinated sanctions on Russia.
Cooper is currently attending the Munich Security Conference alongside Prime Minister Sir Keir Starmer, where the pair have been calling for European allies to be ready to fight, particularly against threats from Russia.
