British police say they are treating the death of London-based Russian businessman Nikolai Glushkov as a homicide, after a post-mortem revealed he died from compression to the neck.

Glushkov was an associate of Boris Berezovsky, a Russian oligarch and Kremlin critic who died under disputed circumstances in 2013.

Glushkov, 68, was found dead at his south London home on Monday. The death came a week after former Russian spy Sergei Skripal and his daughter Yulia were left critically ill from a nerve agent poisoning in the city of Salisbury.

Police say "at this stage, there is nothing to suggest any link to the attempted murders in Salisbury," nor any evidence that Glushkov was poisoned.

They say counterterrorism detectives are leading the case "because of the associations Mr. Glushkov is believed to have had."