WASHINGTON -- Iran's detention of two British-owned oil tankers in the Strait of Hormuz sharply escalated tensions with London and Washington on Friday, increasing the odds that the two allies would undertake new military steps to protect shipping in the strategically important Middle East waterway.
Naval forces from the Iranian Revolutionary Guard Corps seized the British-flagged tanker Stena Impero, claiming it failed to follow international maritime regulations while transiting the strait, according to Iran state media.
The tanker "was seized by the IRGC due to violating international regulations," the Revolutionary Guard said in a statement. "After it was seized it was transferred to Iranian shores to undergo legal procedure."
Another tanker was boarded by armed Iranian naval forces on Friday but later allowed to proceed, according to the Iranian news service FARS. The ship, named the Mesdar, is Liberian-flagged but operated by Norbulk Shipping, a U.K.-based company.
The Iranian moves caused oil futures to spike and sharply raised fears in jittery markets that escalating tit-for-tat actions by Tehran, Washington and London could threaten the flow of oil through the strait and possibly lead to military confrontation, as much as all sides appear to be trying to avoid one.
Officials in Washington and London held back from threatening military action to free the tanker Friday, and several senior officials said the U.S. would likely take its cue from Britain in deciding how to respond.
Britain's Cabinet convened an emergency session in London to weigh options for securing the release of the Stena Impero, Foreign Secretary Jeremy Hunt said.
"I'm extremely concerned by the seizure of two naval vessels by Iranian authorities in the Strait of Hormuz," Hunt said in a statement.
"We are working closely with international partners," he added. "These seizures are unacceptable. It is essential that freedom of navigation is maintained and that all ships can move safely and freely in the region."
The vessel's owner said it had been seized in international waters while headed toward port in Saudi Arabia. "We are presently unable to contact the vessel, which is now heading north toward Iran," the company said.