Five armed Iranian Islamic Revolutionary Guard Corps (IRGC) boats attempted to seize a British oil tanker in the Persian Gulf on Wednesday, U.S. news agency CNN reported.
CNN cited two U.S. officials as saying that the British Heritage tanker was sailing out of the Persian Gulf and was crossing into the Strait of Hormuz area when it was approached by the IRGC boats.
The officials said the Iranians ordered the tanker to change course and stop in Iranian territorial waters.
The U.K.'s Royal Navy frigate HMS Montrose, which was escorting the tanker, is equipped with 30mm guns specifically designed to drive off small boats.
The officials said its crew trained the deck guns on the Iranians and gave them a verbal warning to back away, which they subsequently did.
A U.S. aircraft flying overhead recorded the incident, CNN said.
The incident follows a warning Wednesday by Iranian President Hassan Rouhani that the U.K. will face “repercussions” for seizing an Iranian oil tanker last week off the coast of Gibraltar.
The British government said the tanker was believed to be carrying two million barrels of crude oil to Syria in breach of European Union sanctions against the Bashar al-Assad regime.
Iran has denounced the tanker’s seizure as "piracy" and summoned the British envoy in Tehran to protest the action, denying that the tanker was bound for Syria.
On Tuesday, Tehran vowed to respond to the seizure of the tanker "at an appropriate time and place".