Royal Marines have boarded an oil tanker after it was believed to be breaching EU sanctions whilst on its way to Syria.
The ship is the Panamanian-registered Grace 1, which was carrying 2 million barrels of crude oil to the Banias Refinery in Syria.
The oil originated in Iran and was on its way when a tip-off led Royal Marine commandos, police and customs officers to board the tanker around two miles off Gibraltar.
Both the cargo and crew have been detained.
The UK Government has welcomed "firm action by the Gibraltarian authorities'':
"This sends a clear message that violation of the sanctions is unacceptable."
The refinery is subject to European Union sanctions against Syria, the Chief Minister of Gibraltar said.
Speaking to Forces News, Fabian Picardo explained the rules and regulations which set out the legality and conditions of detention periods.
He also remarked that Gibraltar does not recognise any sanctions against Iran.
"We are not dealing with any issues that deal with the origins of this oil," said Mr Picardo.
Watch: Fabian Picardo says the situation is "a simple legal issue".
"The simple legal issue," he said, "is that there is a sanction regime adopted by a law of the European Union. It is a Council regulation. Council regulations are directly effective on all the member states."
"The only thing that the states have to do is to have laws to give effect to those regulations."
Foreign Secretary Jeremy Hunt said the "bold move" by Gibraltar and the Royal Marines had denied valuable resources to Bashar Assad's "murderous regime".