The death of a 68-year-old Russian man in London is being investigated by counter-terrorism officers, Scotland Yard has said.
While officers are not naming him, he is believed to be businessman Nikolai Glushkov, who was top of a list of "fugitives from justice" published by the Russian embassy which accused him of committing "severe financial offences".
Scotland Yard said anti-terror police were investigating his death "as a precaution because of associations that the man is believed to have had".
But it said there was "no evidence to suggest a link to the incident in Salisbury", adding that the death was being treated as "unexplained".
One of Mr Glushkov's friends was late Russian oligarch Boris Berezovsky, who fled to London in 2000 following a row with Vladimir Putin.
Mr Glushkov, a former deputy director of the Russian airline Aeroflot, had also worked for Mr Berezovsky's LogoVAZ car company.
After Mr Berezovsky was found hanged in the bathroom of his Berkshire home in March 2013, Mr Glushkov told The Guardian he would "never believe" his friend took his own life.
An inquest into Mr Berezovsky's death recorded an open verdict.
Mr Berezovsky was also a friend of Russian dissident Alexander Litvinenko, who was poisoned with radioactive polonium-210 in London in 2006.
Police and MI5 are expected to examine allegations that a series of deaths on UK soil, including the Berezovsky case, may be linked to Russia.
Sky News' home affairs correspondent, Mark White, said Mr Glushkov's home in New Malden, southwest London, was being treated as a crime scene. Officers were called by the London Ambulance Service at 10.46pm on Monday.
Local resident Tracy Broadfield said the police presence was "very large".
Neighbour Patricia Egan said Mr Glushkov had lived there for several years, describing him as well educated and "a lovely fellow".
"His daughter used to call – she was in her 20s I think," she added.
The body was removed at about 8.15pm on Tuesday and taken away in a private ambulance.
Mr Glushkov was arrested in 1999 and put on trial for allegedly embezzling $7m from Aeroflot, and sentenced in 2004 to three years, three months in prison.
Russian media said he was granted political asylum in Britain in 2010.
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But his case was revived by a Moscow court last year, which sentenced him in absentia to eight years for allegedly embezzling more than $122m from Aeroflot.
The Russian embassy said it had sought Mr Glushkov's extradition in 2015 "for committing a number of severe financial offences on the territory of Russia", but the British government refused.