Al Qaeda's deputy leader Mr Ayman al-Zawahri called on Muslims to attack the West in an audio tape posted on the Internet on Saturday, urging similar strikes as those against New York, London and Madrid in recent years.
He also called on Muslims to boycott countries which had published satirical cartoons of the Prophet Mohammad, including Denmark, Norway, France and Germany, and said that Muslims should prevent the West from "stealing Muslims' oil".
"(Muslims have to) inflict losses on the crusader West, especially to its economic infrastructure with strikes that would make it bleed for years," said the speaker on the tape, who sounded like Mr Zawahri, an Egyptian doctor.
"The strikes on New York, Washington, Madrid and London are the best examples," he said.
"We have to prevent the crusader West from stealing the Muslims' petroleum which is being drained in the biggest robbery in history," he added.
The authenticity of the tape could not be independently verified, but it was posted on Web site that is frequently used by Islamist groups.
As well as physical attacks on the West, Mr Zawahri, who is deputy to al Qaeda's leader Osama bin Laden, called for an economic boycott against several countries.
"It is our duty to take part in a mass economic boycott of Denmark, Norway, France, Germany, and all countries that take part in this crusader attack against Islam," he said, referring to the cartoons first publishd in a Danish newspaper last year.
The speaker described the cartoons as part of a US-led "crusader" campaign, intimating at a religious war.
"An example of the hatred of the crusaders led By America ... are the repeated offences against the personality of the Prophet Mohammad, may peace be upon him," the speaker said.
Saturday's tape came as US President George W Bush concluded a visit to Pakistan, where Mr Zawahri and Bin Laden are believed to be hiding.
Mr Zawahri, in a tape aired by the Qatar-based Al Jazeera satellite channel in January, described Mr Bush as a "butcher" and said a recent US air strike in Pakistan targeting him had killed only innocent people.