A cargo ship contracted by U.S. Military Sealift Command fired warning shots at two Iranian speedboats that came within a few hundred yards of the vessel as it transited through international waters in the Persian Gulf, a U.S. defense official said.
The Iranian craft turned away from the vessels after the shots were fired.
The incident occurred Thursday morning as the SS Westward Venture entered the Persian Gulf with its military cargo, according to the official.
At 8 a.m., two unidentified boats approached the cargo ship. As the boats drew closer, the crew aboard the cargo ship warned the ships by radio to stop their approach and later flares were fired to escalate the warnings, the official said.
Finally, warning shots were fired in the direction of the approaching craft. The two Iranian craft turned away after the shots were fired. There are no indications that the boats were hit by the warning shots, a U.S. official said.
"The purpose of warning shots is to let them know they're getting too close and not to hit the vessel," said Cmdr. Lydia Robertson, a spokeswoman for US Naval forces in the region.
A short time after the incident, the Westard Venture received a radio query from a vessel identifying itself as an Iranian Coast Guard ship.
The query was normal in nature, asking the U.S. ship to properly identify itself. The Navy doesn't know whether this transmission came from one of the two Iranian speedboats or from another Iranian vessel in the vicinity, a defense official said.
It is standard procedure for cargo ships contracted by Military Sealift Command to have security teams aboard as they transit through the region. The crew fired rounds from their 50-caliber machine guns and M-16 rifles, according to the official.
This is the second incident in the last 30 days in which a U.S. military-contracted cargo ship has been involved in an incident that resulted in warning shots being fired at approaching craft.
In late March, in the Gulf of Suez off the coast of Egypt , the MV Global Patriot fired warning shots in front of vessels carrying merchants hawking their wares.
The Navy later apologized after it became evident that the shots had in fact struck the boat and killed one of the merchants aboard.
Thursday's incident is the latest brush with Iranian vessels in the gulf.
Earlier this month the USS Typhoon fired a warning flare at a small Iranian boat after it came within 200 yards of the ship.
In January, several Iranian boats made reportedly provocative moves around three U.S. ships as they passed through the Strait of Hormuz.
In December the USS Whidbey Island fired warning shots at a small Iranian boat rapidly approaching the ship.