From the AP:

A civilian ship working for the U.S. military fired warning shots at two small boats that approached it in the Persian Gulf, the U.S. Navy said Friday.

The Western Venture was in international waters in the central Gulf on Thursday morning when it was approached by two small boats of unknown origin, said Cmdr. Lydia Robertson, a spokeswoman for the U.S. Navy’s Fifth Fleet.

“Following proper procedures, Western Venture issued standard queries to the small boats via bridge-to-bridge radio but received no response,” said Robertson. “Western Venture then activated a flare but again did not receive a response.”

The small boats continued toward the ship, and the ship’s security team fired warning shots with .50-caliber machine guns and M-16s into the water in front of the boats, causing them to leave the area, said Robertson.

A unit that identified itself as an Iranian Coast Guard vessel radioed the Western Venture a short time after the incident to determine its identity, said Robertson.

“It is not clear if this was one of the small boats or a separate boat,” Robertson said.