Authorities in the British territory of Gibraltar say they have arrested the captain and chief officer of an Iranian supertanker they seized last week.

The authorities said on Thursday that they also confiscated documents and electronic devices from the vessel. They added that the tanker would remain in detention for further investigations.

Gibraltar is located near the southern tip of the Iberian Peninsula. Its authorities seized the tanker on July 4. They suspect the ship was carrying crude oil to a refinery in Syria in violation of EU sanctions on the administration of President Bashar al-Assad.

Iran denies the allegation. It has been demanding the immediate release of the tanker and its crew, saying the seizure of the vessel is illegal.

Iran's Revolutionary Guard Corps also indicated it would take retaliatory action.

NHK