West, a UK ship insurer, said that it would be difficult to pay claims for ships involved with accidents or collisions involving other vessels insured by the sanctions-hit Russian Ingosstrakh. This is another indication of the difficulties with Moscow's oil trading.

Ingosstrakh provides insurance for ships to Russian oil exporters. The British government added the company to its list of Russian entities sanctioned by the UK in June.

West is one of 12 clubs that offer protection and indemnity coverage for ships. This covers claims from third parties, including environmental damage or injury. Around 90% of ocean-going tonnage is covered by the 12 P&I Clubs that make up the International Group of P&I Clubs.

In an advisory issued this week, West stated that it may be limited in its ability to cover members for any liabilities they might incur with another vessel insured through Ingosstrakh.

It said that this is particularly true when it is a planned operation, such as the transfer of oil from ship to ship.

In the event of an accident with a vessel insured by Ingosstrakh, West said that "the club's members are advised that it may be necessary to obtain a license to pay or reimburse any liabilities resulting from the collision".

It may take some time to get a license, if it is possible at all.

Ingosstrakh did not respond immediately to a comment request. The company had previously stated that it could challenge the UK sanctions in court.

In a note published in July, Jonathan Moss wrote that the UK aims to stop Ingosstrakh from providing insurance coverage for the shadow fleet vessels, which were largely provided by Ingosstrakh. This will make it more difficult for these ships access ports.

According to estimates, up to 850 oil tanks are part of the shadow fleet that transports oil from countries like Iran and Venezuela along with Russia which has many restrictions on its oil imports. Reporting by Jonathan Saul, Moscow Bureau