Iran has now seized an Iraqi tanker that it had earlier towed following a distress call over the weekend.

State television quoted Iran's Revolutionary Guards as saying it had held the 1,800-dwt Riah (built 1988) over alleged fuel smuggling.

"A foreign vessel smuggling 1m litres of fuel in the Lark Island of the Persian Gulf has been seized," the report said.

The vessel was held on Sunday, it added.