TEHRAN, Iran — 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.

The incident comes after a U.S. Navy patrol boat fired warning shots Tuesday near an Iranian vessel that American sailors said came dangerously close to them during a tense encounter.

Iran and the U.S. frequently have run-ins in the Persian Gulf, nearly all involving the Revolutionary Guard, a separate force from Iran’s military that answers only to the country’s supreme leader. In January, near the end of then-President Barack Obama’s term, the USS Mahan fired shots toward Iranian fast-attack boats as they neared the destroyer in the Strait of Hormuz.

Iranian forces view the American presence in the Gulf as a provocation. They have accused the U.S. Navy of unprofessional behavior, especially in the Strait of Hormuz, the mouth of the Persian Gulf through which a third of all oil trade passes by sea.