Two Bermuda-registered superyachts owned by the Russian billionaire Roman Abramovich could be seized after they put into port in the Caribbean.

The 67-metre Garçon and the 55-metre Halo, flying the Bermuda flag, docked in Falmouth Harbour in Antigua, which said it was prepared to co-operate with Britain, the EU and the United States, which have imposed sanctions on Russian oligarchs after Russia launched an invasion of neighbouring Ukraine.

Sir Ronald Sanders, Antigua and Barbuda’s ambassador to the US, said: “Antigua and Barbuda has been at the forefront of objections to the invasion of Ukraine and Russia’s violation of international law.”

But he added the US had been unable to establish beyond doubt the ownership of the boats because of the “veil of secrecy” around BVI companies.

Sir Ronald said: “We have no sanctions laws here — we can’t seize property unless someone has committed a crime in Antigua, which they have not.

“However, we would wish to co-operate with the jurisdiction imposing the sanctions.

“The British would have to make a mutual legal assistance treaty request to Antigua for us to do anything.”

Sir Ronald explained that once a request was made, the case could be taken to court for a possible seizure of the boats.

He was speaking to the Antigua Observer, which said that the British Financial Times had identified the yachts as linked to Mr Abramovich.

The two yachts were said to be owned by British Virgin Islands-based Wenham Overseas and that Abramovich, 55, was the beneficial owner.

But firms based in BVI, like Bermuda, a UK Overseas Territory where John Rankin, a former governor of Bermuda, is the Governor, are not required to reveal the beneficial owners.

But E P Chet Greene, the Antigua and Barbuda foreign affairs minister, has written to Scott Furssedonn-Wood, the British High Commissioner to Barbados, who also has responsibility for several other Caribbean countries, to ask for assistance in firm identification of the boats’ owner and to promise “full assistance”.

Britain, the EU and the US have drawn up sanctions lists of the Russian super-rich and companies linked to them said to be close to Russian president Vladimir Putin, who ordered the illegal invasion of Ukraine.

Mr Abramovich, the owner of Chelsea FC in London, and other Russian oligarchs have been hit with asset freezes, travel bans and other restrictions.

Several megayachts, along with private aircraft and mansions, have been seized by authorities around the world.

Antigua and Barbuda joined the chorus of condemnation of the illegal Russian action in Ukraine and promised to take action against Russian interests.

Sir Ronald said: “We gave the lists to all our agencies, banks, Coast Guard, shipping companies, everyone who does business, saying these are people Antigua and Barbuda would prefer not to do business with.”

The country has warned that anyone caught doing business with people or companies on the sanctions list, even if by accident, risked sanctions themselves.

The Antigua Observer said that the country’s banks had decided not to do any business with Russia or Belarus, which has supported the Russian invasion, even if the people or firms were not on any sanctions list.

Sir Ronald explained: “Going through every single person on the lists is expensive and the risk was not worth the reward.”

Lindsy Thompson, the resident British Commissioner in the two-island country, said: “It’s incredibly important for all nations, regardless of the size of their population, to put pressure on Russia.

“The horrific invasion and atrocities being committed by Russia have a profound effect on the whole world, whether it’s the cost of fuel, the cost of living, but also on each nation’s right to self-determination and this is a huge affront to that.”

Ms Thompson added: “Anything any country can do which allows the people of Ukraine to live in peace is the right thing to do.“

The Bermuda Shipping and Maritime Authority revealed two weeks ago that ten vessels on the island’s registry belonged to companies set up in other overseas territories that were “widely known to be associated with high-profile Russian nationals”.

The BSMA said there was nothing in Bermuda’s maritime legislation to allow for sanctions.

But the authority was said to be in consultation with the Attorney-General’s Chambers and the Financial Sanctions Implementation Unit to decide the next steps.