One of top five

Khalid Sheikh Mohammed is one of its top five leaders. Now United States intelligence officials are in a race to make him talk.

The hours and days following his capture are crucial in order to uncover the identity and whereabouts of Al Qaida cells around the the world before they disappear or carry out major acts of terrorism in revenge for his arrest.

As Al Qaida's principal military and operational commander, he is likely to know the whereabouts of Osama bin Laden as well as the planning for new terror attacks.

Western diplomats said there is a danger that operations in the planning stage could now be swiftly carried out by Al Qaida because groups in Europe and the United States would fear being exposed by Mohammed as he is interrogated.

"His arrest will cause a huge disruption in the international terrorist network and many people will be trying to move out of their present locations and houses," said a Western diplomat in Islamabad.

"We may have a chance to grab them if we know where they are. It's a huge opportunity, but it has to be done quickly," he added.

European diplomats and security officials said that it was intelligence that Mohammed was planning "something big", which triggered the enormous security alerts in Britain and the United States last month, when troops were stationed at Heathrow airport for several days and Washington declared a heightened "orange alert".

"Mohammed knew everyone who passed through Al Qaida camps in the past 10 years and he knows everyone who is still free and out there ready to carry out more terrorist attacks," said a European security official.

In Afghanistan, he would select the most promising Al Qaida recruits for advanced training so that they could be sent abroad and planted in Western societies.

It is widely believed in the intelligence community that Mohammed was a chief planner, organiser and financier of the September 11 attacks. From his base in Kandahar he co-ordinated the activities of the Hamburg cell that carried out the suicide attacks. He also travelled to Hamburg at least once to meet with Mohammed Atta – the gang leader.