LONDON -- A Russian exile, who was close friends with the late Russian oligarch Boris Berezovsky, has been found dead in his London home, British media reported Tuesday.

Nikolai Grushkov, 69, was found dead by his family at his home in New Malden in south London on Monday evening, Daily Mail reported.

Without disclosing the deceased man's name, London's Metropolitan Police said in a statement that an investigation is underway following the death of a man in his 60s in Kingston borough and formal identification has to be carried out.

The police said they were called by the London Ambulance Service on Monday night to reports of a man found deceased at a residential address.

A post-mortem examination will be held in due course and the death is currently being treated as an unexplained, the police said.

"At this stage, the Met Police Counter Terrorism Command is leading the investigation as a precaution because of associations that the man is believed to have had," the police said in statement, stressing that there is no evidence to suggest a link to the incident in Salisbury.

Glushkov's death came a week and a day after fellow Russian exile Sergei Skripal and his daughter Yulia were critically injured in a nerve agent attack in Salisbury.

British Prime Minister Theresa May on Monday pointed her finger at Russia over a developing "poisoning attack" row, claiming that her government had concluded it was "highly likely" that Moscow was responsible for the attack.

May told the parliament that Russia's ambassador in London had been summoned to explain whether it was "a direct action by the Russian state" or the result of it "losing control" of its stock of nerve agents.

British Home Secretary Amber Rudd said police and the security services would investigate allegations of Russian state involvement in a number of deaths over recent years in Britain.

In a letter made public Tuesday, Rudd says the government takes seriously allegations that some 14 deaths may have some links to Russia.

"In the weeks to come, I will want to satisfy myself that the allegations are nothing more than that," Rudd said. "The police and MI5 agree and will assist in that endeavor."