A US Navy ship has rescued 13 Iranians held hostage by Somali pirates for weeks in the Arabian sea, US military officers said Friday. The USS Kidd, a destroyer, responded to a distress call from an Iranian-flagged fishing vessel and a Navy team boarded the boat, freeing the Iranian crew and detaining 15 suspected pirates, the Fifth Fleet said in a statement. The incident was an unexpected twist after days of rising tensions between Iran and the United States, with Tehran issuing threats and warning the Americans not to send the USS John C. Stennis aircraft carrier through the Strait of Hormuz. But one of the ships accompanying the Stennis, the USS Kidd, came to the rescue Thursday of Iranians on the fishing dhow Al Molai, whose captain issued a call on for help saying \"he was being held captive by the pirates,\" said the statement from the Fifth Fleet, based in Bahrain. \"A visit, board, search and seizure team from Kidd boarded the Al Molai and detained 15 suspected pirates who had been holding a 13-member Iranian crew hostage for several weeks,\" it said. \"The Al Molai had been pirated and used as a \'mother ship\' for pirate operations throughout the Persian Gulf, according to members of the Iranian vessel\'s crew,\" it said. The detained pirates -- who were believed to be Somalis -- were being held on the Stennis, said a Pentagon spokesman, Captain John Kirby. \"The Iranians and the dhow have been released and are on their way back home,\" Kirby told AFP. Prior to Thursday\'s rescue, another Iranian vessel, a motor boat, had issued a distress call while under suspected attack from pirates. A helicopter from another Navy ship also assigned to the Stennis carrier group, the USS Mobile Bay, responded to the call for help, he said. But the pirates threw objects into the water and \"they boarded the skiff and couldn\'t detain the pirates because there was no evidence,\" he said.