The Al Qaeda network may be driven by an extremist religious 'brain trust', operating behind the scenes and providing its followers with ideological underpinnings for terrorist attacks, according to counter-terrorism expert K P S Gill, who is credited with wiping out militancy from Punjab.

"It is a brain trust bent on world conquest, Islamic conquest," Gill said in a speech at the American Foreign Policy Council in Washington.

Echoing Gill's view, a senior US official was quoted by the Washington Post saying that the idea of a 'secret religious hierarchy behind the Al Qaeda network' was being investigated.

One key piece of evidence was the videotape obtained in Afghanistan, in which Al Qaeda chief Osama bin Laden is seen explaining the September 11 attacks, the official said.

On the tape, Laden spoke as though reporting to a Saudi cleric named Al Ghamdi.

Investigators are probing whether Al Ghamdi is connected to a network of Islamic extremist religious leaders who are behind Al Qaeda, the official said.

PTI