The seizure of a VLCC off Gibraltar by British forces on Thursday has prompted a furious reaction in Iran.

The 301,000-dwt Grace 1 (built 1997) was boarded by marines after they had reason to believe the tanker was carrying Iranian crude to Syria in breach of European Union and US sanctions.

The Independent reported that Iran has threatened to seize a UK tanker unless the ship is released.

The country’s Revolutionary Guards commander Mohsen Rezaee said on Twitter on Friday it was Iran’s “duty” to act in the same manner as the British.

'Unacceptable seizure'

"Islamic Iran in its 40-year history has never initiated hostilities in any battles but has also never hesitated in responding to bullies,” he added.

The 28 crew are being interviewed as witnesses, not criminal suspects, authorities in Gibraltar said.

On Friday, Gibraltar’s Attorney General secured an order from the Supreme Court extending the period of detention of the ship by 14 days.

The territory was allowed to hold it for 72 hours initially.

The Supreme Court granted the order after a hearing In private.

“The Supreme Court has issued today’s order on the basis that there are reasonable grounds to consider that the detention of the Grace 1 is required for the purposes of compliance with the EU regulation 36/2012 on sanctions on Syria,” the government said..

The Daily Telegraph said Iran had summoned the British ambassador to the foreign ministry in Tehran to express "its very strong objection to the illegal and unacceptable seizure".

Abbas Moussavi, an Iranian spokesman, called the move "destructive" and said it could increase tensions in the Middle East Gulf following attacks on six tankers blamed on Iran by the US.

A police investigation is ongoing. The ship is still at anchor and the crew are still on board but are being interviewed at this stage by Royal Gibraltar Police and Her Majesty’s Customs officers

HM Government of Gibraltar

Moussavi told Iranian television the move was "a form of piracy" that proved Britain was following "the hostile policies of the US".

Crude allegations

The government of Gibraltar said authorities suspected the 301,000-dwt Grace 1 (built 1997) was carrying crude to the Banias refinery, the BBC reported.

It told TradeWinds: "A police investigation is ongoing. The ship is still at anchor and the crew are still on board but are being interviewed at this stage by Royal Gibraltar Police and Her Majesty’s Customs officers."

There are no longer any marines onboard.

The government added that the 28 crew are mainly Indian nationals, though there are some Ukrainian and Pakistani nationals too.

The vessel is listed as managed by Iships of Singapore.