War risk insurers for a VLCC seized and held for more than a year by Iran have refused to pay the Greek owners their $49m claim because of concerns of breaching US sanctions.

Iranian troops backed by fast patrol boats and helicopters seized the 309,000-dwt VLCC Niovi (built 2005) in May 2023 because of a three-year-old dispute over an alleged Iranian oil cargo as it was passing through Oman territorial waters, according to court papers.