British police have launched a murder inquiry after a Russian exile was found dead in his London home earlier this week.
Nikolai Glushkov, 69, was found dead on Monday night (local time), as a result of "compression to the neck", police say, according to The Guardian.
Meanwhile a war of words has intensified between Britain and Russia, as blame is thrown over the poisoning of an ex-spy and his daughter living in London three weeks ago.
A counter-terrorism command unit is leading the investigation into Mr Glushkov's death "because of the associations the man is believed to have had", Metropolitan police said on Tuesday.
Mr Glushkov is believed to have been close friends with Russian businessman Boris Berezovsky, a reported enemy of Vladimir Putin.
When he died, he was preparing to defend a fraud claim put against him by Russian airline Aeroflot.
In 1999 he was jailed for a five-year term for fraud and money-laundering.
There is no evidence linking his death to the poisoning of ex-spy Sergei Skripal, who remains in a critical condition alongside his daughter after the pair were slipped a suspected nerve agent.
Mr Skripal was once a colonel in Russia's GRU military intelligence service, but had been secretly working for the UK since the mid-1990s. He was arrested by the Russians in 2004, but handed over to the UK in 2010 as part of a spy swap.