July 5 (UPI) -- A top adviser to Iranian leader Ayatollah Ali Khamenei on Friday encouraged forces to seize a British oil tanker as a response to London's taking an Iranian supertanker off the coast of Gibraltar.
British Royal Marines detained the Iranian vessel Thursday because officials said it was transporting oil to Syria, a violation of European Union sanctions. The Grace 1 tanker was boarded and detained by Marines off the British territory on the southern tip of Spain, Gibraltar minister Fabian Picardo said in a statement.
Officials said the seizure resulted from information the Gibraltar government received that gave it "reasonable grounds" to suspect the vessel was violating EU sanctions.
Friday, Iran Expediency Council Secretary Mohsen Rezaee said a British tanker should be taken in retaliation. Rezaee demanded the Iranian ship's immediate release and called those who seized it "bullies and thugs."
"If Britain doesn't return the Iranian tanker, the duty of responsible [Iranians] is to seize a British oil tanker in a retaliatory measure," he said.
Josep Borrell, Spain's acting foreign minister, said the United States had asked Britain to detain the ship.
Iran Foreign Ministry spokesman Abbas Mousavi said via Twitter British Ambassador Robert Macaire was summoned to his office over the "illegal seizure." In a statement, the Foreign Ministry said it told Macaire the detainment was "tantamount to maritime banditry" and demanded its release.
U.S. national security adviser John Bolton called the seizure "excellent news."
"America & our allies will continue to prevent regimes in Tehran & Damascus from profiting off this illicit trade," he said in a tweet, stating that Grace 1 was "laden with Iranian oil."
The Panama-flagged vessel was loaded with 2 million barrels in Iranian waters mid-April, shipping journal Lloyd's List reported. It cited tracking data and said the Grace 1 employed tactics used by tankers shipping Iranian oil to China and Syria.
Tanker Trackers reported the Grace 1 left Iran April 17, traveled around the southern tip of Africa and was heading through the Strait of Gibraltar between Spain and Morocco when it was seized.
"Their swift action has denied valuable resources to Asad's murderous regime," he said, referring to Syrian President Bashar al-Assad.
The incident came as tensions rise between the United States and Iran, primarily over U.S. sanctions that have stifled Tehran's oil industry. The conflict worsened following attacks on several tankers in the Gulf of Oman, which the United States blamed on Iran.
Iran in May partly withdrew from the 2015 nuclear deal and has been growing its stockpile of low-enriched uranium. Last week, it surpassed the limit set by the Obama-era agreement.
Iranian President Hassan Rouhani on Wednesday threatened to take steps closer to producing a nuclear weapon if a trade deal doesn't come by Sunday.