London (AFP) - The Russian embassy in London said Wednesday it had asked British authorities for details about a Russian who died in mysterious circumstances, amid a diplomatic crisis over an attack on an ex-spy.
Nikolai Glushkov, a former senior executive linked to late Kremlin opponent Boris Berezovsky, was found dead in his home in the southwest of the capital on Monday, Russian and British media said.
The embassy made an official request for information on the "mysterious" case.
"The investigation is not transparent, the British side appears not inclined to cooperate. This can only cause regret," it said.
"Today the embassy made an official request to provide all the information in possession of the British side regarding this Russian citizen whose death, as you said, appears mysterious."
Police have confirmed they are treating the death of an unnamed man found in the southwest suburb of New Malden on Monday as "unexplained".
They have called in counter-terror officers "as a precaution because of associations that the man is believed to have had", a spokesman said Tuesday.
Glushkov received political asylum in Britain after serving five years in prison in Russia for money laundering and fraud, the Guardian reported.
His death has prompted speculation because it occurred in the middle of a crisis between Russia and Britain over the attempted murder of former Russian double agent Sergei Skripal on March 4.
British Prime Minister Theresa May earlier Wednesday said Moscow was "culpable" for the attack in the southwestern city of Salisbury, and expelled 23 Russian diplomats.
Police are revisiting a number of other unexplained deaths following the Skripal case.
Yvette Cooper, who chairs the House of Commons home affairs committee, has raised 14 cases that have reportedly been identified by US intelligence sources as potentially connected to Russia.
These include oligarch Berezovsky, a one-time supporter of Russian President Vladimir Putin who then turned against him, and was found hanged in a bathroom at his home outside London in 2013.
Another is businessman Alexander Perepilichny, who was found dead in front of his London home in 2012, and which Foreign Secretary Boris Johnson said last week was "deeply troubling".
In a letter to Cooper, Home Secretary Amber Rudd said: "In the weeks to come, I will want to satisfy myself that the allegations are nothing more than that.
"The police and MI5 (domestic spy agency) agree and will assist in that endeavour."