Oleg Erovinkin, who served as a general in the KGB, was found dead on Boxing Day in the back of his black Lexus in Moscow

The Kremlin may have covered up the murder of a former KGB chief accused of helping ex-MI6 spy Christopher Steele to pull together the notorious dossier on Donald Trump.

Oleg Erovinkin served as a general in the KGB and was found dead on Boxing Day in the back of his car in Moscow.

It has been claimed he died of a heart attack, but an expert on Russian security threats believes he was murdered for his role in the explosive dossier.

The suspected murder victim was close to former deputy prime minister Igor Sechin, who is named throughout the leaked memo, according to the Telegraph.

Erovinkin is understood to have been an important link between Sechin and leader of the Kremlin Vladimir Putin.

Agent Steele's dossier, which was made public earlier this month, noted how he had a source close to Sechin.

Igor Sechin and Russian President Vladimir Putin pictured attending a meeting on January 25

Donald Trump speaks with Vladimir Putin on the telephone in the Oval Office on January 28

He said the source had revealed alleged links between the US President's supporters and Moscow.

At the time of Erovinkin's death, Russian state-run RIA Novosti news agency said his body was found in a black Lexus and that a major investigation was underway in the area.

His body was sent to the morgue, which returned no cause of death, and the investigation continues.

Local media reports suggested he was killed as a result of foul play, but it was later claimed he died of a heart attack.

Christo Grozev, an expert on Russia-related security threats, wrote in a blog post, that he believes Erovinkin was Mr Steele's dossier source.

He wrote that he has no doubt the dossier was on Putin's desk at the time the suspected victim died.

'Whichever is true,' he wrote, 'He would have had a motive to seek – and find the mole.

Christopher Steele pictured with a female companion believed to be his second wife Katharine

'He would have had to conclude that Erovinkin was at least a person of interest.'

The so-called dirty dossier states that in 2013 Trump hired prostitutes to urinate on the bed of the Presidential Suite at the Moscow Ritz Carlton, where he knew Barack and Michelle Obama had previously stayed.

It says: 'Trump's unorthodox behavior in Russia over the years had provided the authorities there with enough embarrassing material on the now Republican presidential candidate to be able to blackmail him if they so wished.'

The document states that Trump had declined 'sweetener' real estate deals in Russia that the Kremlin lined up in order to cultivate him.

The business proposals were said to be 'in relation to the ongoing 2018 World Cup soccer tournament'

The dossier claimed that the Russian regime had been 'cultivating, supporting and assisting Trump for at least five years'.

According to the document, one source even claimed that 'the Trump operation was both supported and directed by Russian President Vladimir Putin' with the aim being to 'sow discord'.

The report claims that Russian President Vladimir Putin himself had endorsed moves to encourage 'splits and divisions in the West.

The dossier was handed over to the FBI in August although the information was also passed from the former MI6 agent to John McCain through an intermediary.

McCain then handed the document over to FBI Director James Comey.

Its contents were made public after intelligence chiefs apparently briefed Trump and Obama on the allegations which were circulating in Russia and elsewhere.

However, none of the claims have been proven and most are strongly denied by the President-elect.