an extremely large ship-tanker at sea

Islamic Revolutionary Guards Corps, Iran’s paramilitary, has seized a British-flagged and a Liberian-flagged oil tanker traveling through the Strait of Hormuz on Thursday, Britain’s foreign secretary said, in what appeared to be a significant new escalation between Tehran and Western countries.

Late Friday, a management company for the Liberian tanker, Mesdar announced in a statement that “the armed guards have left and the vessel is free to continue the voyage. All crew are safe and well.”

Foreign Secretary Jeremy Hunt said in a statement he was “extremely concerned by the seizure of two naval vessels by Iranian authorities.”

Iran’s State TV said on Saturday that the British tanker was seized after it collided with a fishing vessel and ignored calls from the smaller craft.

Late Friday evening, following meetings in Washington, D.C., with more than 60 foreign ambassadors, U.S. Central Command (CENTCOM) announced a U.S.-led maritime security initiative dubbed Operation Sentinel “to increase surveillance of and security in key waterways in the Middle East to ensure freedom of navigation in light of recent events in the Arabian Gulf region.”

The initiative, according to CENTCOM, “will nations to provide escort to their flagged vessels while taking advantage of the cooperation of participating nations for coordination and enhanced maritime domain awareness and surveillance.” The statement does not specify the nations that have joined the coalition.

The British tanker, the Stena Impero, was crossing through the strait when it abruptly changed course and headed north towards Iran’s Qeshm island, ship tracking sites showed.