Iran has summoned the British ambassador in Tehran over the "illegal seizure" of an Iranian oil tanker in Gibraltar, the official government news agency IRNA quoted Foreign Ministry spokesman Abbas Musavi as saying on July 4.
Britain’s Foreign Office confirmed the move and said the ambassador will reiterate Britain’s support for Gibraltar’s seizure of the ship, which was accused of bringing oil to Syria in violation of European Union sanctions.
The government in the British overseas territory said that British Royal Marines boarded the supertanker, called the Grace 1, on July 4.
The vessel is suspected of carrying crude oil to Syria’s Banias refinery, which is subject to EU sanctions.
"We have reason to believe that the Grace 1 was carrying its shipment of crude oil to the Banyas refinery in Syria," Gibraltar's Chief Minister Fabian Picardo said in a statement.
"That refinery is the property of an entity that is subject to European Union sanctions against Syria.
"We have detained the vessel and its cargo," Picardo said.
Acting Spanish Foreign Minister Josep Borrell told Spanish news media that the vessel was detained at the request of the United States.
Picardo said he had "written this morning to the presidents of the European Commission and council, setting out the details of the sanctions which we have enforced."
Data from Refinitiv Eikon, an industry source of data on tanker traffic, indicates the cargo sailed from Iran, according to Reuters.
If the tanker is confirmed to have been carrying Iranian crude, its attempted delivery to war-torn Syria could also be a violation of U.S. sanctions on Iran's oil exports.
The Grace 1 is a 300,000-ton, Panamanian-flagged tanker managed by a Singapore-based company, shipping data shows.
A spokesman for British Prime Minister Theresa May said she welcomed the "firm action" by the authorities in Gibraltar.
Spanish Foreign Minister Josep Borrell said the Grace 1 was detained after a request by the United States to Britain.
Iran, along with Russia, has given crucial support to Syrian President Bashar al-Assad throughout Syria’s civil war -- now in its ninth year.
The conflict, which began with a government crackdown on protesters in March 2011, has killed more than 370,000 people and displaced millions.