By Agence France-Presse London wants to de-escalate tensions with Tehran, Foreign Secretary Jeremy Hunt said Saturday following a meeting of the UK's emergencies committee over Iran's seizure of a British-flagged ship in the Gulf. Britain's Foreign Secretary Jeremy Hunt. (AFP / MANILA BULLETIN) The meeting "reaffirmed UK desire to de-escalate," Hunt said, adding that the Stena Impero oil tanker was seized in Omani waters "in clear contravention of international law" in "utterly unacceptable" circumstances. The seizure came hours after a court in the British overseas territory of Gibraltar said it would extend by 30 days the detention of Grace 1, an Iranian tanker seized two weeks ago in an operation aided by British Royal Marines on allegations of breaching EU sanctions against Syria. Hunt said that having spoken to his Iranian counterpart Mohammad Javad Zarif, Tehran saw the situation as a "tit for tat". "Nothing could be further from the truth," he said. "Grace 1 was detained legally in Gibraltarian waters because it was carrying oil, against EU sanctions, to Syria, and that's why the Gibraltarian authorities acted totally with respect to due process and totally within the law. "Stena Impero was seized in Omani waters in clear contravention of international law. It was then forced to sail into Iran. "This is totally and utterly unacceptable. It raises very serious questions about the security of British shipping, and indeed international shipping, in the Strait of Hormuz." Hunt said parliament would be updated on Monday about what further measures the British government would take. "Our priority continues to be to find a way to de-escalate the situation," he said. Hunt said the Stena Impero must be released, and Britain was "very concerned" about the safety of the 23 crew. The Philippines said 18 Indians, three Russians, a Latvian and a Filipino were aboard the Swedish-owned ship.