DUBAI: Iran's coast guard has detained two Saudi fishing vessels after they entered Iranian waters, the semi-official Fars news agency reported on Tuesday.

Separated by about 250 km (150 miles) of Gulf waters, Shiite 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 Shiites 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.

Fars quoted Lashkari as saying that the two dhows were tracked and confiscated after they illegally entered Iran's territorial waters.

All their 10 crew were arrested, it said. Initial investigations showed that the vessels were from Saudi Arabia but their captains and crews were Indian nationals, Fars said. They had crossed into Iranian waters to fish, the agency said.

A week earlier, Fars said, forces of the Iranian Revolutionary Guards' "second naval zone" seized another Saudi vessel and its four-strong crew after it illegally entered Iranian waters. The vessel was later expelled, the agency said, without elaborating.

On Jan. 3, Saudi Arabia detained 21 Iranian nationals who were aboard two boats near al-Harqus island 42 miles (78 km) off the Saudi coast, the Saudi border guard said.