Terror chiefs have called on militants to destroy tankers bound for the west by ramming them with boats laden with explosives or by hijacking the ships and running them aground.
An attack would cause “phenomenal” reaction around the world and help ramp up oil prices, shipping rates and maritime insurance as well as military spending.
British oil workers in the Middle East are also legitimate targets according to the new Al Qaeda magazine, Resurgence, released last week.
A spokesman for the Government of Gibraltar told the Sunday Express: “This is not the first time that threats have been made to target merchant shipping passing through the Straits of Gibraltar.
“Defence and security in British Gibraltar Territorial Waters is the responsibility of the United Kingdom Government and not of the Government of Gibraltar.
“Having said that, it is only to be expected that those responsible for security in the region will take every precaution possible.”
The Ministry of Defence confirmed last night it was aware of the threats and would act accordingly.
Every year 106,000 ships, including 5,000 oil tankers bound for the West, pass through the Strait.
Watching over The Rock is the Royal Navy’s Gibraltar Squadron, equipped with two fast patrol boats, HMS Sabre and HMS Scimitar, and three Pacific 24 rigid-hulled inflatable boats, manned by a team of 22.
In an article entitled On Targeting The Archilles Heel Of Western Economies, Al Qaeda leaders urge Mujahideen fighters on the Moroccan side of the Strait to strike.
They encourage a coordinated attack on oil tankers off Gibraltar as well as other “chokepoints” around the world, including the Strait of Hormuz between Oman and Iran, the Suez Canal in Egypt, the Malacca Straits in Malaysia and the Turkish Straits.
Of Gibraltar, the magazine notes: “The Strait forms the opening of the Mediterranean into the Atlantic.
“At its narrowest point, the Strait is 7.7 nautical miles (14.3km wide).
“On the Spanish side of the Strait, Britain maintains a permanent military presence in the form of the British Enclave at Gibraltar.
“Oil tankers from the Red Sea or the Suez Canal that are destined for Western Europe or the United States pass through the Strait.”
An Al Qaeda cell suspected of plotting raids on British and American ships and tankers passing through the Strait of Gibraltar was arrested in June 2002 by the Moroccan government.
Later that year, Al Qaeda rammed a boat filled with explosives into a badly holed French supertanker off the coast of Yemen.
Damage to the global economy due to piracy at sea amounts to nearly £10billion, the Resurgence article reports.
Al Qaeda has vowed numerous times, to cut the “economic lifelines” of the world’s industrialised nations but the latest threat comes during an upsurge of terrorist activity around the world.
Last week, Canada was reeling from two lone-wolf terror attacks, which claimed the lives of two soldiers and sparked a shoot-out in the country’s Parliament.
Resurgence is the latest instalment in glossy English-language publications produced by terrorist groups.
IS produced a similar magazine called Dabiq in July, focusing mainly on the group’s caliphate in Iraq and Syria.
The fight against IS has seen Jihadists flock from all over the world.
However, last week it emerged that biker gangs from the Netherlands and Germany had travelled to Syria to fight against the fundamentalists.
Members of the Median Empire Motorcycle Club, from Germany and the Dutch No Surrender Motorcycle Club have travelled to the region to help the Kurds in their battle against IS.