Iran’s elite Revolutionary Guard said Saturday a U.S. Navy aircraft carrier fired a warning shot in an “unprofessional” confrontation with Iranian vessels, the official IRNA news agency reported.

IRNA quoted a statement from the Guard as saying that the USS Nimitz and an accompanying ship came near an Iranian oil offshore platform in the Persian Gulf and a helicopter from the ship hovered near vessels manned by Iran’s elite Revolutionary Guard.

The report said the confrontation took place Friday afternoon and the U.S. navy ships left the area following the encounter. The U.S. Navy’s Bahrain-based 5th Fleet had no immediate comment. Iran and the U.S. frequently have run-ins in the Persian Gulf.