Al Qaeda has advised followers to attack pipelines in Saudi Arabia and Iraq but to steer clear of oil wells because they are the lifeline of Muslim states, according to a two-year-old document recently posted on the Web.
The guidelines in al Qaeda's war against "crusaders" and US-allied governments were laid out in a manifesto written by Abdulaziz al-Enezi, arrested in Saudi Arabia in 2005 and described by the Saudis as a prominent ideologue of al Qaeda.
In the manifesto, which was recently posted on an Islamist Web site, Enezi said disrupting oil supplies was the best way to hurt the US economy and destabilise the Saudi royal family.
The document said Saudi state-owned refineries and oil pipelines and Iraqi facilities were "all in the hands of infidels."
"It is permissible to target oil interests held by infidels ... including American and Western oil tankers," Enezi said.
Saudi Arabia, the world's top oil exporter, has since 2003 been battling al Qaeda militants bent on toppling the pro-US monarchy and expelling Westerners from the birthplace of Islam.
Al Qaeda claimed a foiled suicide attack on an oil facility last week in the kingdom and vowed more attacks in response to a call by al leader Osama bin Laden to target oil installations.
The attempted assault on the world's largest oil processing plant at Abqaiq was the first direct attack on a major oil Saudi target and sent jitters through international oil markets.
Fares bin Houzam, an expert on al Qaeda, told Reuters that Enezi had been considered Saudi al Qaeda's "information minister" and a spiritual guide to the group.
Enezi said oil pipelines were the easiest targets because they were hard to protect, less costly to fix and attacks on them did not rob Muslims of their oil wealth.
"Targeting oil pipelines is of huge benefit in spiting the enemies ... pipelines may well be the frontline in a long-term war of attrition on oil and its interests," he said.
In Iraq, repeated attacks by insurgents on pipelines in the north have made it difficult for the country to boost its oil exports, the main source of government revenue.
Enezi said government-owned refineries and oil plants were also good targets. But the al Qaeda idealogue said oil wells should be avoided because any attack on them would cause economic and environmental damage to the people of the country.
"The wells will be needed when the Muslim nation is victorious and retakes its possessions and would be very costly to repair," he said.
A successful strike on the Saudi oil industry would be a major coup for al Qaeda, hitting at the heart of a decades-old US-Saudi alliance, and a nightmare for oil consumer nations as the kingdom accounts for around a sixth of the world's exports.
Analysts have said that the kingdom's security measures would make it very difficult for militants to stage a successful attack on vital oil installations in the Gulf Arab state.