The British Royal Marines and Gibraltar officials detained Grace 1 supertanker for the suspicion of transporting oil to Syria.

The Gibraltar officials confirmed the report on Wednesday, saying the 300 thousand-ton supertanker was flying the flag of Panama and was headed to Banyas oil refinery in Syria, which “is the property of an entity that is subject to European Union sanctions against Syria”.

According to maritime intelligence company data, the oil tanker had loaded its cargo in Iran.

Iran has summoned the British ambassador in Tehran, claiming the seizure of the tanker is illegal. 

Ever since the civil war began in Syria, the Islamic Republic has been supporting the Assad regime financially and militarily. After the civil war, the Assad-controlled parts of Syria have been faced with energy shortage.

Earlier this year, Reuters published a report naming four tankers including Grace 1 as the biggest tankers that carry Iranian oil to Singapore and China, evading U.S sanctions.

U.S sanctions on Iran have reduced the country’s oil export from 2.7 million barrels a day to under 300 thousand barrels a day. Iran is therefore trying to find alternative ways to evade the sanctions.