The US Navy said its sailors and the United Kingdom Royal Navy came to the aid of a ship in the crucial Strait of Hormuz after “Iranian fast-attack boats harassed it.”

The internationally flagged merchant vessel made a radio distress call while transiting the narrow strait. Three fast-attack craft with armed personnel approached and followed the merchant vessel at close distance, the US Navy said in a statement.

The US Navy claims that the fast-attacked craft were assessed to be from the Iranian Islamic Revolutionary Guard Corps Navy.

The US Navy’s guided-missile destroyer USS McFaul and the Royal Navy’s frigate HMS Lancaster responded to the incident, with the Lancaster launching a helicopter.

“The situation de-escalated approximately an hour later when the merchant vessel confirmed the fast-attack craft departed the scene,” the Navy said. “The merchant ship continued transiting the Strait of Hormuz without further incident.”

A previous incident occurred one month ago when the Islamic Republic of Iran Navy seized Marshall Islands-flagged oil tanker Advantage Sweet while it transited international waters in the Gulf of Oman.

However Iran’s Navy said at that time that has seized an “offending Marshall Islands-flagged” ship in the Sea of Oman, after it allegedly collided with an Iranian boat and attempted to flee the scene, according to Islamic Republic News Agency IRNA. It added that “the Iranian naval forces had later intercepted the fleeing ship in the Sea of Oman and directed it toward Iran’s coastal waters.”