A supertanker which is suspected of carrying crude oil to Syria has been detained by Gibraltar for acting in violation of European Union sanctions, the territory's chief minister said Thursday.

Gibraltar port and law enforcement agencies, aided by British Royal Marines, detained the Grace 1 tanker in the early hours of Thursday morning.

“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 the statement.

“That refinery is the property of an entity that is subject to European Union sanctions against Syria.”

The Syrian government has not yet responded to the incident.