Separated by about 250 km (150 miles) of Gulf waters, Shi'ite Muslim power Iran and Sunni Muslim-led Saudi Arabia have often had tense relations. Saudi Arabia, a U.S. ally, has accused Iran of fomenting unrest among Shi'ites in its oil-rich Eastern Province, a charge Iran denies.

Fars did not give a date or location for the incident but said it was reported by Qalandar Lashkari, the coast guard commander at Bushehr, which is both a province and a port town on Iran's Gulf coast. It is also the site of the only nuclear power station in the Islamic Republic.