War risk insurers have refused to pay the Greek owners of a VLCC seized and detained by Iranian armed forces for over a year their $49m claim, citing concerns about violating 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.