Iranian patrol boats intercepted a cargo ship in the Strait of Hormuz April 28 and forced it into Iranian territorial waters by firing shots across its bow.
The move, denounced as "inappropriate" and "provocative" by the Pentagon, prompted the U.S. Navy to send a destroyer and reconnaissance plane to monitor the situation.
Iranian Revolutionary Guard boats confronted the MV Maersk Tigris, a Marshall Islands-flagged vessel, as it was traversing one of the world's most important oil shipping channels and forced it to divert toward Larak Island near Bandar Abbas, where it was boarded by Iranian forces, U.S. officials said.
The incident shook world markets and drove up the price of oil on April 28. Almost one third of the world's traded oil passes through the narrow Hormuz strait, which connects the oil-rich Gulf to the Indian Ocean. The ship was en route from Saudi Arabia's Red Sea port of Jeddah to the United Arab Emirates port of Jebel Ali in the Gulf.
The incident was the second such Iranian interception of a cargo ship in four days and came amid heightened tensions in the region as Saudi Arabia and its Gulf allies wage a campaign of air strikes in Yemen against Iranian-backed Huthi rebels. Saudi jets bombed the airport in Yemen's capital on April 28 to prevent Iranian planes from landing.
The seizing of the Maersk Tigris came just four days after Iranian patrol boats surrounded a U.S.-flagged vessel, the Maersk Kensington, and followed it in the same area, a U.S. official said. No warning shots were fired in that incident.
Iranian officials sought to play down the ship seizure, saying it was a civil matter with no military or political dimension.
Mohammad Saidnejad, head of Iran's Ports and Maritime Organization, said a court in Tehran had given the order to seize the ship, with at least 24 crew members hailing mostly from eastern Europe and Asia. "A legal complaint from an Iranian private company resulted in the seizure of a Marshall Islands-flagged ship in Iranian waters," Saidnejad was quoted as saying by Iranian news agency IRNA.
In the April 28 incident, the intercepted ship was traveling through the narrow Strait, which is technically Iranian and Omani territorial waters, but under international agreement is open to foreign ships making an innocent passage, said Colonel Steve Warren, a Pentagon spokesman. It wasn't clear whether the ship had strayed off course into coastal waters not protected by that agreement.
The master of the cargo ship MV Maersk Tigris had initially refused an Iranian order to move further into Iranian waters, but after the warning shots were fired the vessel complied, Warren said.
The cargo ship was directed to waters near Larak Island, which sits off the major Iranian port of Bandar Abbas, he said.
"It is inappropriate" for the Iranians to have fired warning shots across the ship's bridge, Warren said. He added it was too early to know whether the Iranian intervention amounted to a violation of the freedom of navigation through a waterway heavily used by international shipping.
The spokesman said the U.S. government has "certain obligations" to defend the interests of the Marshall Islands, but he was uncertain how those obligations to the Pacific Ocean nation apply in this situation.
The Iranian vessels, numbering five or six, were with the Iranian Revolutionary Guard Corps Navy, he said.
After the cargo ship sent a distress call, the U.S. Navy sent the destroyer USS Farragut and a Navy maritime patrol and reconnaissance aircraft to the area of the incident to monitor the situation, Warren said.
With reporting by Reuters, AFP, and AP