UK police have launched a murder investigation into the death of a London-based Russian businessman after an autopsy found he died from “compression to the neck”.

Nickolay Glushkov, 68, was found dead in his home in the south-west London suburb of New Malden on March 12 and at that stage the cause of death was treated as “unexplained”.

Police said a post-mortem was conducted on Thursday and a pathology report released on Saturday (Friday local time) gave the cause of death as compression to the neck.

Mr Glushkov was a Russian associate of the late tycoon Boris Berezovsky, 67, who was found dead in the bathroom of a luxury West London home in 2013 with a scarf tied around his neck. He was known as the “godfather of the Kremlin” before fleeing to London in 2000 after a row with Russian leader Vladimir Putin.

The Met Police’s Counter Terrorism Command, which has led the investigation into Mr Glushkov from the outset, is now treating his death as murder. As a precaution, the command is retaining primacy for the investigation because of the associations Mr Glushkov is believed to have had.

The murder investigation comes as police continue to investigate the attempted murder of former double agent Sergei Skripal, 66, and his daughter Yulia, 33, who remain in hospital in a critical condition since March 4, when they were found unconscious on a bench in the southern English cathedral city of Salisbury.

In an angry address on Tuesday (Monday local time) British Prime Minister Theresa May told the UK Parliament that it was “highly likely” Moscow was behind the attempted murder.

She told MPs the chemical used in the attack was identified as being part of a group of nerve agents known as Novichok, a military-grade substance developed by Russian scientists.

“Either this was a direct action by the Russian state against our country, or the Russian government lost control of its potentially catastrophically damaging nerve agent and allowed it to get into the hands of others,” Ms May said.

Russian Foreign Ministry spokeswoman Maria Zakharova said Ms May’s statement was “a circus show in the British parliament”.

“The conclusion is obvious – it’s another information and political campaign based on provocation,” she was quoted as saying by the BBC.

Earlier, asked whether Russia was to blame, President Vladimir Putin told the BBC: “Get to the bottom of things there, then we’ll discuss this”.

Mr Glushkov’s family has been informed. Photo: Metropolitan Police UK

UK’s Metropolitan Police said Mr Glushkov, a retired financial director, was a Russian national who had lived at that address for two years.

“At this stage there is nothing to suggest any link to the attempted murders in Salisbury, nor any evidence that he was poisoned,” the statement said, adding there were no “wider public health concerns” in relation to the investigation.

Boris Johnson points finger directly at Putin

In the latest war of words between the two countries, UK’s foreign secretary Boris Johnson said it was “overwhelmingly likely” Russian President Vladimir Putin ordered the nerve-agent attack, the BBC reported.

During a visit to a west London military museum on Saturday (Friday local time), Mr Johnson said the UK’s “quarrel is with Putin’s Kremlin”.

“We think it overwhelmingly likely that it was his decision to direct the use of a nerve agent on the streets of the UK, on the streets of Europe, for the first time since the Second World War,” he said.

Russia denies involvement and said the accusations against Mr Putin were “shocking and unforgivable”, reported the BBC.