MV Maersk Mc-Kinney Moller,
The MV Maersk Mc-Kinney MollerReuters

A senior US navy official has denied reports on Iranian state media and Saudi-owned Al-Arabiya news site that Iran seized a US cargo ship with its 34 crew and forced it into an Iranian port for "trespassing" on territorial waters.

The Pentagon told Reuters that Iranian forces boarded the Marshall Island-flagged MV Maersk Tigris in the Gulf and no Americans were on board.

Earlier, the Saudi channel had reported that an Iranian "force" had opened fire on a US cargo ship and then directed it to the Iranian port of Bandar Abbas.

Iran's semi-official Fars news agency said the vessel had been detained "for trespassing on Iran's territorial waters".