Qatar's al Jazeera television has aired what it says is an audio tape purportedly from Osama bin Laden's top aide in which he urges Muslims to intensify their holy war against Americans and Jews.
In the recording, which appears to be have been made in the early days of the US-led war on Iraq, Ayman al-Zawahri also told Muslims to strike at the missions and commercial interests of the United States, Britain, Australia and Norway in and "turn the ground beneath their feet into an inferno".
He told the Iraqi people that they were "not alone" in fighting what he called the US occupation of their country.
"The crusaders and the Jews only understand the language of murder, bloodshed... and of the burning towers," he said referring to New York's World Trade Center twin towers, levelled by suicide plane hijackers on September 11, 2001.
"Carry arms against your enemies, the Americans and Jews... Attack the missions of the United States, UK, Australia and Norway and their interests, companies and employees," he added.
Considered to be bin Laden's right-hand man, Egyptian eye doctor Zawahri founded a militant group which tried to topple the Egyptian government in the 1990s.
Bin Laden's al Qaeda is blamed for the September 11 attacks as well as triple suicide bombings in Riyadh last week which killed 34 people, mainly foreigners.
Last October, al-Jazeera broadcast the alleged voice of Zawahri speaking on the anniversary of the US-led war in Afghanistan.