Russian political exile Nikolai Glushkov was found dead in London on Monday night.
British police said he was murdered, killed by a compression to the neck.
The 69-year-old previously said he was part of a Kremlin hit-list.
The anti-Putin Russian exile who was found dead in London earlier this week was murdered, British police have confirmed.
Nikolai Glushkov, 69, was found dead at his house in southwest London around 10:46 p.m. on Monday. A subsequent pathologist report found that Glushkov died by a "compression to the neck," London's Metropolitan Police said on Friday.
Glushkov was best known for being a close associate of Russian oligarch and prominent Putin critic Boris Berezovsky, who was found dead on the bathroom floor of his ex-wife's house in Ascot, southeast England, in 2013.
Shortly after Berezovsky's death, Glushkov told The Guardian that he was also a target of the Russian government.
He alleged that Berezovsky and Alexander Litvinenko, a former Russian spy who was killed in 2006 with polonium poison, had both been on a Kremlin hit-list.
Glushkov said at the time: "I don't see anyone left on it apart from me."
On Wednesday, Glushkov's friend Alex Goldfarb also claimed that Russian intelligence agencies had held a grudge against Glushkov since the 1990s.
Glushkov was granted asylum in the UK in 2010. The Russian national previously worked at Berezovsky's car company LogoVAZ and Russian state airline Aeroflot, from which he was convicted of stealing $100 million last year.
He had been expected in commercial court on the morning of his death to defend a claim made against him by Aeroflot. An unidentified friend told The Guardian that Glushkov "had been getting ready for this for months."
British counterterrorism officers are leading the investigation "as a precaution" because of Glushkov's associations.
They added that there was "nothing to suggest any link" to the attempted assassination of ex-spy Sergei Skripal in Salisbury, who is the subject of a diplomatic dispute between Moscow and London.