The U.S. Navy says a Coast Guard vessel has fired in self-defense on an Iranian boat in the Persian Gulf, and that no Americans were wounded in the encounter.

U.S. 5th Fleet spokesman Cmdr. Kevin Stephens said Wednesday the crew on a small boat dispatched from the U.S. Coast Guard patrol boat Monomoy fired a single shot when it saw crew on the Iranian dhow preparing to fire a .50-caliber machine gun.

Stephens says the incident happened in international waters at around 11:30 a.m. local time Tuesday. It was not clear if the shot hit the Iranian vessel or if anyone onboard was injured.

American, Iranian and other countries' military vessels routinely patrol the Gulf. Dhows are traditional wooden boats that are typically used for trade.