Authorities had accused the Grace 1 supertanker of illegal smuggling as it had reportedly been transiting some 2 million barrels of Iranian oil.
Iran's foreign ministry had immediately summoned the UK ambassador over the incident, saying the move was "unacceptable". An official statement of protest called for "the immediate release of the oil tanker, given that it has been seized at the request of the US, based on the information currently available," the statement added.
Iran's position is that the EU sanctions on Syria have not been endorsed by the UN, while the US received the news as a positive development in the global crackdown on Iranian oil. "Excellent news: UK has detained the supertanker Grace I laden with Iranian oil bound for Syria in violation of EU sanctions," John Bolton said on Twitter.