Dubai, United Arab Emirates -- Britain said Thursday that three Iranian vessels had unsuccessfully tried "to impede the passage" of a British commercial vessel transiting the Strait of Hormuz, but Tehran denied it. A statement issued by the British Ministry of Defense said a Royal Navy warship, the frigate HMS Montrose "was forced to position herself" between the Iranian vessels and the oil tanker, called the British Heritage.
The crew of the Montrose issued "verbal warnings to the Iranian vessels, which then turned away," according to the British government statement, which added that London was "concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region."
CBS News national security correspondent David Martin said no shots were fired and the British Heritage continued on its way through the Strait of Hormuz, a vital water waterway that connects the Persian Gulf with the rest of the world via the Gulf of Oman. A third of the world's shipped oil supply passes through the Strait every year, and Iran has threatened to halt that traffic in previous standoffs with the West.
Martin said the British Heritage was intercepted by Iranian "fast boats," small vessels used frequently by the Revolutionary Guard to harass commercial ships in the Persian Gulf and the Strait of Hormuz.
Iran's Revolutionary Guard denied the allegations, saying if it had received orders to seize any ships it would have executed them immediately.
The semi-official Fars news agency carried a statement from the Guard's navy early Thursday saying "there were no clashes with alien boats, especially English boats."
Iran's Foreign Minister Mohammad Javad Zarif dismissed the British allegations as "worthless," saying the claims were "being made to create tension," the agency reported.
Russia, meanwhile, which has backed Iran in the standoff with the West over its nuclear program, blamed the U.S. for the incident on Thursday.
"The situation is very concerning," Russian Deputy Foreign Minister Sergei Ryabkov said according to Russia's state-run media. "The reasons for this are clear. This is Washington's deliberate, premeditated course to exacerbate tensions."
Kremlin spokesman Dmitry Peskov told journalists he was aware that "such an incident allegedly took place" but also of Tehran's denial. "As before, we call on everyone to behave with restraint in the Persian Gulf in order not to exacerbate the situation," he said.
A senior U.S. defense official told Martin that he expected all British tankers transiting the Persian Gulf would now sail with U.K. military escort vessels.
The British Heritage is listed on the website of U.K. petrochemical giant BP as part of its fleet. The Century Class oil tanker is one of the largest crude oil tankers in BP's fleet. BP owns and operates three vessels of the same class. They can carry up to a million barrels of oil at a time and a crew of about 25 officers, according to the BP website.
The incident was reported a day after Iran's president, Hassan Rouhani, warned that Britain would face unspecified "repercussions" for the British military's seizure last week of an Iranian supertanker that authorities in Gibraltar say was breaching European sanctions on oil shipments to Syria.
Rouhani was quoted by Iranian state media as saying the seizure was "mean and wrong."
Zarif, the Foreign Minister, denied the supertanker belonged to Iran, saying whoever owned the oil shipment and the vessel could pursue the case through legal avenues.
Iran had earlier summoned the British ambassador over what it called the "illegal interception" of the ship.
The incident marked the latest escalation ofin the wake of President Trump's unilateral withdrawal of the U.S. from the 2015 nuclear deal between Iran and world powers.