British counterterrorism police overnight took charge of the investigation into the death in London of a Russian businessman because he was connected to a prominent Kremlin foe.
The death of Nikolai Glushkov, confirmed by his lawyer in Russia, came a week after former spy Sergei Skripal was left critically ill from nerve agent poisoning in the city of Salisbury.
Police said there was no evidence to suggest a link to the March 4 poisoning of Skripal and his daughter Yulia.
Attorney Andrei Borovkov told Russian media outlets that Glushkov had died, but said he was unaware of the time and circumstances.
Reports in British and Russian media said Glushkov, who was in his late 60s, was found dead at his home in southwest London.
London's Metropolitan Police force said it was investigating the unexplained death of a man found at a house in the New Malden area late Monday (Tuesday NZT).
It didn't release his name, saying formal identification had yet to take place.
Police said counterterrorism detectives are leading the investigation "as a precaution because of associations that the man is believed to have had."
Glushkov was an associate of Boris Berezovsky, a Russian oligarch and Kremlin critic who died in London in 2013. An inquest failed to determine whether he had killed himself or died from foul play.
Glushkov told The Guardian newspaper in 2013 he didn't believe Berezovsky's death was suicide.