Grace 1 a Panama flagged oil tanker was detained in Gibraltar at the request of the US. It was suspected of transporting oil to Syria, despite sanctions against that country, and  was intercepted on Thursday, July 4 off the coast of Gibraltar at the request of the United States, said Spanish Foreign Minister Josep Borrell.

"We are studying the circumstances in which this has occurred, which has been a request that the United States sent to the United Kingdom," Borrell told reporters.

The authorities of the British territory of Gibraltar, located in the southern tip of Spain, assisted by a detachment of Royal Marines, stopped the oil tanker on Thursday morning about four kilometers south of the "Rock".

"Naturally we were aware of this operation, the patrol boats of the Civil Guard have been securing the area," said Borrell.

"We are seeing how it affects our sovereignty, because it has occurred in waters whose sovereignty

we understand belongs Spain," he added.

Gibraltar considers that the waters are under British jurisdiction, a claim questioned by Spain, which says it sovereignty over the territory.

The Panamanian freighter is suspected of transporting oil to Syria, violating sanctions imposed on Damascus.

The Gibraltar authorities did not specify the origin of the oil, but the specialized maritime publication Lloyd's List said that it was a freighter with Iranian oil.