The widow of murdered Russian spy Alexander Litvinenko thinks the Russian government may have been involved in the murder of leading opposition figure Boris Nemtsov.

Marina Litvinenko told BBC Radio on Sunday she thinks Nemtsov's slaying Friday night in Moscow seems to have been the Russian government's way of silencing critics of President Vladimir Putin, but offered no proof. She said the Russian government has become particularly aggressive since the Ukraine crisis began. She called Nemtsov's death "absolutely devastating."

Putin has condemned the killing of Nemtsov and said he will lead the official inquiry into it.

Marina Litvinenko has blamed the Russian government for the poisoning of her husband, who died in London in 2006 after ingesting radioactive tea. An inquiry into her husband's death is ongoing.