Al-Qaeda leader Osama Bin Laden has become, in US eyes, the world's most wanted man, and the subject of constant speculation as to his whereabouts.
The most recent intelligence on Bin Laden has been revealed following the capture of alleged al-Qaeda mastermind Khalid Sheikh Mohammed in Pakistan.

Investigators believe he kept in contact with Bin Laden through e-mails and hand-delivered messages. They hope items seized during the 1 March raid could lead them to Bin Laden.

Since the 11 September attacks, numerous video tapes, audio recordings, faxes and other statements have been attributed to Bin Laden.

The US has also thrown some of its best resources into hunting the al-Qaeda leader, using satellite tracking systems and sophisticated spying systems.

However the last reliable intelligence on the al-Qaeda leader appears to be from November or December 2001 during the US-led bombing of Afghanistan, when US forces apparently intercepted radio messages in which he was directing troops from the mountainous region of Tora Bora.

In February 2003 an audio tape purporting to be by Bin Laden in which he called for attacks on US and British targets if Iraq was to be attacked was broadcast.

In November last year a tape surfaced on Arabic TV station al-Jazeera. A speaker, which voice experts identified as belonging to Bin Laden, referred to attacks in Bali, Yemen and the Moscow siege last November, indicating he was alive at least until the end of the siege.

However Bin Laden's network suffered a blow in September 2002 when an alleged planner of the 11 September attacks, Ramzi Binalshibh, was captured in the Pakistani city of Karachi.

His capture led to speculation that other senior al-Qaeda leaders - including Bin Laden - may be seeking shelter in Pakistan, particularly in the tribal border region close to Afghanistan.

For much of last year, information and intelligence on Bin Laden grew sparse, and it emerged in May that troops from the US-led coalition in Afghanistan had begun collecting human DNA samples in the Afghan mountains of Tora Bora to establish whether he had died there.

In April 2002 old clips of Bin Laden and some of his top aides, were aired on al-Jazeera, along with footage of an 11 September hijackers reading what appeared to be his suicide note.

Frustrated with the lack of progress, US officials admitted in December 2001, three months after the 11 September attacks, that they had no information on the al-Qaeda leader's whereabouts.

Al-Jazeera released more footage of Bin Laden, in which he refers to the 11 September attacks, and the US Government warns that any foreign country found harbouring the wanted Saudi dissident would suffer the consequences.

In November 2001 a letter, alleged to be from Bin Laden, calls on Muslims in Pakistan to stand up for Islam as the country supports the US-led campaign against Afghanistan.

And in October 2001, Bin Laden warns in a statement - broadcast on al-Jazeera two hours after the US-led coalition begins military strikes against Afghanistan - that it will have no rest until the Middle East conflict is resolved and US military bases in the region are shut down.

He does not claim responsibility for the 11 September attacks, for which President Bush has put him top of the list in the FBI's "Most Wanted" list, with a $25m award for information regarding his whereabouts.