LONDON: UK Ministry of Defense said that Iranian boats had tried to impede a British oil tanker near the Gulf.
However, the tanker was driven off by a Royal Navy ship.
HMS Montrose, a British frigate shadowing the tanker British Heritage, was forced to move between the three boats and the tanker, a spokesman said.
He described the Iranians’ actions as “contrary to international law”.
Iran had threatened to retaliate for the seizure of one of its own tankers, but denied any attempted seizure.
Boats believed to belong to Iran’s Islamic Revolution Guard Corps (IRGC) approached British Heritage and tried to bring it to a halt as it was moving out of the Gulf into the Strait of Hormuz.
Guns on HMS Montrose were trained on the Iranian boats as they were ordered to back off, US media reported. The boats heeded the warning and no shots were fired.
The British Heritage was near the island of Abu Musa when it was approached by the Iranian boats.
Although Abu Musa is in disputed territorial waters, HMS Montrose remained in international waters throughout.
A UK government spokesman said: “Contrary to international law, three Iranian vessels attempted to impede the passage of a commercial vessel, British Heritage, through the Strait of Hormuz.
“We are concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region.”
International Trade Secretary Liam Fox thanked the crew of HMS Montrose, adding: “It is our duty as a parliament to ensure that all those forces are adequately resourced.”
Quoting the public relations office of the IRGC’s Navy, the Fars news agency said, in a tweet, the IRGC “denies claims by American sources” that it tried to seize British Heritage.
“There has been no confrontation in the last 24 hours with any foreign vessels, including British ones,” the IRGC added.