Police have moved in to evict squatters who had occupied a London mansion suspected of belonging to Russian billionaire Oleg Deripaska.

Mr Deripaska was put on Britain’s sanctions list last week in response to Russia’s invasion of Ukraine.

Wearing riot gear, officers entered the multimillion-pound mansion, which the squatters had earlier occupied, in Belgrave Square in an upmarket area of London and home to numerous foreign embassies.

However, they remained in a stand-off with the squatters who gathered on the balcony at the front of the property where they had unfurled a Ukrainian flag and placed a banner reading “This property has been liberated”.

“You occupy Ukraine, we occupy you,” said a statement from the squatters, who described themselves as anarchists.

“By occupying this mansion, we want to show solidarity with the people of Ukraine but also the people of Russia who never agreed to this madness.”

Police said they had searched the property and were satisfied there was no one inside.

“We continue to engage with those on the balcony as we balance the need for enforcement with the safety of all involved,” police said on Twitter.

Britain froze Mr Deripaska’s assets last Thursday. He is one of several Russian oligarchs targeted after the invasion of Ukraine, which the Kremlin has called a “special military operation”.

Mr Deripaska, who has stakes in energy company En+ Group – which owns one of the world’s major aluminium producers UC Rusal – is worth an estimated £2 billion ($A3.6 billion) and has a multimillion-pound property portfolio in Britain, the British government said at the time.

Britain said Mr Deripaska is closely associated with the government of Russia and Russian President Vladimir Putin.

London High Court documents from 2007 identified Mr Deripaska as the beneficial owner of the Belgrave Square mansion.

A judge in a court case the year before said the property and another house he owned outside the capital, were then worth about £40 million.

A spokeswoman for Mr Deripaska said on Monday the property belonged to members of his family.

She accused the British government of colluding with people who raided private property and showing disrespect for the rule of law.

Shortly before the sanctions were imposed, Mr Deripaska said peace was needed as soon as possible in Ukraine and warned that Russia would be different after the conflict.

Britain has so far sanctioned about 20 ultra-wealthy Russian individuals, including Chelsea soccer club owner Roman Abramovich and Alisher Usmanov, freezing their properties across London and banning them from coming to the country.

“Squatting in residential buildings is illegal but we are working to identify the appropriate use for seized properties while owners are subject to sanctions,” a spokesman for Prime Minister Boris Johnson said.

“We certainly don’t think people should break the law.”

-AAP