Nikolai Glushkov, 69, a former deputy director of Aeroflot who had twice faced fraud charges in his native Russian Federation, was found dead at his home in New Malden, south west London, late on Monday night.
Police were called by ambulance services at 10.46 p.m. Monday local time to an address in New Malden, in the borough of Kingston.
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.
London'sMetropolitan Police force 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. Fearing further arrest, he fled to the United Kingdom and was granted political asylum.
His family feared he might have been murdered by enemies in Russian Federation, but British police and forensic experts concluded Berezovsky had committed suicide.
In the 1990s, Glushkov was director of the Russian state airlineAeroflot and Berezovskys LogoVAZ auto company.
There is not now any evidence to link this case to the events in Salisbury where former spy Sergei Skripal and Yulia, his daughter, are still in a critical condition after being poisoned, reports Sky News.
British Prime Minister Theresa May told parliament on Monday that it is "highly likely" that Russian Federation is responsible for the nerve agent attack in Salisbury.
Speaking after Mr Berezovsky's death, Mr Glushkov said: "Too many deaths [of Russian exiles] have been happening".
According to Tass, he received political asylum in the United Kingdom in 2010.
There was no evidence linking the death of the 69-year-old former Aeroflot director, and one-time friend of Mr Berzovsky, to the incidents in Salisbury, police said.
In 2017, a Moscow court reviewed Glushkov's case and sentenced him in absentia to eight years for embezzling more than $122 million from Aeroflot.
The Met said officers believe they know who the man is, but he is yet to be formally identified. "The death is now being treated as unexplained".
A Russian exile found dead in the United Kingdom was being pursued through the London courts over the alleged theft of $123 million from the former state airlineAeroflot.
The inquest heard from Professor Bernd Brinkmann, who said he believed the businessman was strangled by someone else and then hanged from the shower rail in the bathroom.