WASHINGTON — A U.S. Coast Guard cutter rescued six Iranian mariners from a vessel in distress in the Persian Gulf, the second time in less than a week that the American military has come to the aid of Iranians at sea, an official said Tuesday.

Pentagon press secretary George Little said the Iranians aboard a cargo dhow about 50 miles southeast of the Iraqi port of Umm Qasr used flares and flashlights to hail the cutter Monomoy at 3 a.m. local time Tuesday. The vessel’s master indicated that his engine room was flooding and “deemed not seaworthy,” Little said.

Little said one Iranian suffered burn injuries apparently as a result of the engine problem and was receiving medical assistance aboard the Monomoy.

He said it was not immediately clear how the Coast Guard would arrange for the Iranians’ return.

The Monomoy is assigned to a naval task force of the U.S. Naval Forces Central Command.

Last Thursday, the U.S. Navy rescued 13 Iranian fishermen who had been held captive by pirates in the northern Arabian Sea for more than 40 days. That rescue came just days after Tehran warned the United States to keep its warships out of the Persian Gulf. The fishermen were sent on their way, and the 15 pirates were taken aboard the aircraft carrier USS John C. Stennis.