BBC News Online: World: Americas

Bin Laden's command structure

Mr Bin Laden's associates operate in many countries

US officials say they are focusing on more than one group in their hunt for the perpetrators of Tuesday's attacks against New York and Washington.

But it is clear the Saudi-born dissident, Osama Bin Laden, remains a prime suspect.

Mr Bin Laden's organisation is very different from the groups that carried out bombings and hijackings in the past.

It is not tightly knit with a clear command structure. It is a loose coalition of groups operating across continents.

American officials believe Mr Bin Laden's associates may operate in more than 40 countries - in Europe and North America, as well as in the Middle East and Asia.

This has two important consequences for investigators. One is that tracking the people, the front organisations and the financial infrastructure of this network, is an immensely complex task.

The other is that pinpointing the role of Mr Bin Laden himself in any particular operation is often difficult.

He has been described as a "venture capitalist" of Islamic extremism - running "Jihad Inc" and its subsidiary "Jihad-Dot-Com".

A group might come to him with a plan for which he might supply money - or he might put one group in touch with another - or he might come up with a plan of his own and find sub-contractors to carry it out.

To make matters even more complicated, US officials now seem to be looking into the possibility that this week's attacks may have been a co-operative effort.

They may well have in mind the role of Ramzi Yousef, regarded as the mastermind of the last attack on the World Trade Center in New York, in 1993.

He is now in an American jail. Ramzi Yousef has links with Mr Bin Laden and Afghanistan - but he may also have links with the Saddam Hussein government in Baghdad.