The threat of a seaborne terrorist attack on one of Saudi Arabia’s principal oil terminals in the Gulf led today to heightened patrols by an Italian-led coalition naval task force in the area.

Warships were asked to keep a 24-hour watch for any suspicious vessels heading for the Ras Tanura terminal, which is the world’s biggest offshore oil facility after intelligence reports indicating that al-Qaeda was threatening to attack the Saudi terminal or a refinery in Bahrain.

The Royal Navy has one warship in the Gulf at present, HMS Kent, a Type 23 frigate which is armed with a 4.5inch gun that could blast a small vessel out of the water. The warship is part of Coalition Task Force 152 that patrols the international shipping lane.

However, Ministry of Defence sources said although the frigate was in the region, it was not involved in the current force that was guarding the Ras Tanura terminal, which has a capacity to handle six million barrels of oil a day.

Saudi Arabia’s other main offshore oil terminal is at Ras al-Juaymah, also in the Gulf. Both terminals are potentially vulnerable to terrorist attack because they are located in the narrow Gulf waterway which is always filled with shipping and smaller vessels, many of them smuggling craft.

Al-Qaeda has already demonstrated its ability to attack from the sea when a suicide boat blew up outside the port of Aden, creating a huge hole in the American warship, USS Cole, killing 17 sailors in October 2000.

In February al-Qaeda terrorists attempted an attack against the Saudi oil processing facility at Abqaiq. Two-thirds of Saudi Arabia’s crude oil is exported from the Gulf via the Abqaiq facility. The attack failed because of a tight naval security ring around the site.

Since that aborted attack, extra security measures were adopted. Task Force 152, currently headed by the Italians on a command rotation system, also has ships from the United States, France and Germany.

Oil prices jumped about 30 cents to around $61 on the news as traders recalled February's foiled attack.

Today's warning to merchant shipping was made by the UK's Maritime Trade Office in Dubai.

"Coalition, Saudi and Bahraini units in the general vicinity are focusing on presence and deterrence in the approaches to Ras Tanura," the statement said. "Merchant vessels calling at Ras Tanura have been asked to keep a listening watch and to respond as directed to any instructions from Coalition warships."

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