The UK wants action to be taken after evidence showed 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.