Chelsea owner Roman Abramovich arrives for the Champion's League semi-final second leg soccer match against Atletico Madrid at Stamford Bridge in London April 30, 2014.
Chelsea owner Roman Abramovich arrives for the Champion's League semi-final second leg soccer match against Atletico Madrid at Stamford Bridge in London April 30, 2014. Reuters / Toby Melville

Prime Minister Boris Johnson on Wednesday declined to comment on whether Britain would impose sanctions on Russian billionaire Roman Abramovich, but said the "vice" was tightening on those around Russian President Vladimir Putin.

There have been growing calls in Britain for Abramovich, who owns English Premier League soccer club Chelsea, to be included in economic measures taken against Russians who are said to be close to Putin following Russia's invasion of Ukraine.

"He's a person of interest to the Home Office (interior ministry) because of his links to the Russian state and his public association with corrupt activity and practices," opposition Labour leader Keir Starmer said in parliament.

"Last week, the prime minister said that Abramovich is facing sanctions. He later corrected the record to say that he isn't. Well, why on earth isn't he?"

In response, Johnson said he could not go into details on specific cases.

"It's not appropriate for me to comment on individual cases at this stage," Johnson said. "But be in no doubt that the actions that we've already taken ... are having an effect in Moscow by exposing the ownership of properties of companies in the way that we are."

He added: "They will have heard what the president of the United States had to say last night. The vice is tightening on the Putin regime, and it will continue to tighten."

Abramovich's spokeswoman did not immediately respond to a request for comment.

Abramovich, 55, who has Israeli citizenship, was one of the most powerful businessmen who earned fabulous fortunes after the 1991 break-up of the Soviet Union. Forbes has put his net worth at $13.3 billion.

His spokeswoman said on Monday that Abramovich had accepted a Ukrainian request to help negotiate an end to Russia's invasion, which Moscow calls a "special operation", although it was unclear what role he would have.

On Saturday, he said he was giving "stewardship" of Chelsea to trustees of the club's charitable foundation, but gave no details of what that would mean.

Swiss business tycoon Hansjoerg Wyss was reported on Wednesday to be considering buying the club.

"Abramovich is currently trying to sell all his villas in England," Swiss newspaper Blick quoted Wyss as saying. "He also wants to get rid of Chelsea quickly now. I, along with three other people, received an offer on Tuesday to buy Chelsea from Abramovich."

British lawmaker Chris Bryant has told parliament Abramovich was "terrified" of being sanctioned, and was moving to sell his assets, accusing the government of being too slow to act.