Al Qaeda has encouraged its followers to attack oil pipelines and facilities in Muslim countries and tankers but not wells, according to a document posted on a Web site by the group that targeted the world's largest oil-processing complex in Saudi Arabia.

The document was at least a year old, but Al Qaeda's branch in Saudi Arabia posted it earlier this week on an Islamic militant Web forum to show the religious justification for the Feb. 24 attempt to blow up the Abqaiq facility.

"Targeting oil interests is legitimate economic jihad. In this era, economic jihad is one of the best ways to spite nonbelievers," said the document, written by Abdul Aziz bin Rasheed al-Anzy, described by Saudi authorities as one of Al Qaeda's key "ideologues."

Saudi police wounded and arrested al-Anzy in May 2005. The document, though not dated, was written before then. Its authenticity could not be independently confirmed.

"Oil is the basis of modern industry and the backbone of industries in infidel countries. With it, America was able to impose its dominance on the world," al-Anzy purportedly wrote in the 63-page document, titled "The Ruling on Targeting Oil Interests."

"God's wisdom has decreed that the oil wealth be concentrated in the Arabian peninsula and Iraq. This, in addition to some religious reasons, is the reason for the American occupation of Saudi Arabia decades ago and its latest occupation of Iraq."

He continued: "Pipelines may be the front line in a long-term war of attrition on oil and its interests. There is a great benefit in targeting oil pipelines to spite enemies in a way not realized by other means. Pipelines are an easy target militarily. Their protection is virtually impossible because of their length."

Oil facilities and tankers also are fair targets, the document said.

"Targeting refineries and oil factories is not very different from targeting oil pipelines" as long as they are owned by the state or "a nonbeliever," he purportedly wrote.

However, oil wells should not be attacked as long as there are other industry targets.

"The harm caused by targeting oil wells in the lands of Muslims outweigh the benefits because of health and environmental damages and because this will deprive Muslims of the benefit (of the oil wells) when God allows victory," the document said.

Another reason not to attack oil wells, al-Anzy purportedly wrote, was that "the apostate governments exploit these operations to tarnish the image of jihad and mujahedeen.

"The benefits attained by targeting oil wells can be realized by targeting other oil facilities and interests."

He argued that attacks on oil facilities owned by the governments of Muslim Saudi Arabia and Iraq were legitimate, saying those governments are dominated by the United States.

"Oil interests owned by the Muslims include the oil wells that are now in the lands of Muslims such as Saudi Arabia and Iraq as well as the refineries and factories owned by the Saudi government and the oil pipelines in Saudi Arabia and Iraq, which are all in the hands of the nonbelievers," he wrote.

"Targeting oil interests owned by nonbelievers is permissible as long as this will spite and shame them. Oil interests owned by nonbelievers include American and Western oil tankers."

The Saudi Interior Ministry said at the time of al-Anzy's arrest that he was one of the editors of online Al Qaeda periodicals that call for jihad, or holy war, and incite aggression.

The Feb. 24 bombing at Abqaiq was the first attack on an oil facility in the kingdom, which has been battling Al Qaeda militants since 2003 and is the birthplace of Usama bin Laden. That raised fears militants in Saudi Arabia could begin a campaign against the oil infrastructure similar to that launched by insurgents in Iraq — a campaign that has severely hampered the rebuilding of Iraq's vital oil industry.

Suicide bombers tried to crash two explosives-laden vehicles through a gate of the sprawling facility. One collided with the gate, but guards opened fire, detonating them before they could get through, Saudi officials have said.

At least two militants and two security guards were killed.

Days afterward, Saudi security forces launched a raid in Riyadh, killing five militants — including two who were involved in the Abqaiq attack and the leader of Al Qaeda in Saudi Arabia, according to the Interior Ministry.

The Saudi branch of Al Qaeda claimed responsibility for the Abqaiq attack and warned it would continue targeting oil facilities.