So, is Osama bin Laden alive or not?

Al-Qa'ida's leader is rumoured to have died of typhoid last month - but he has come back from the dead before

So is he alive or is he dead? Is he in Pakistan, or Afghanistan, or somewhere else entirely? As usual with Osama bin Laden, there are many questions and few answers.

The latest claim is that the founder and figurehead of al-Qa'ida might have died of typhoid last month in the tribal areas of Pakistan, where he is thought to have been hiding for most of the five years that have elapsed since the 9/11 attacks. But the sourcing was as sketchy as most rumours about Bin Laden: a single uncorroborated French intelligence report, which quoted Saudi security services.

The death of the terror mastermind has been rumoured several times before, only for Bin Laden to prove that he remained at large. On one occasion it was the President of Pakistan himself who started the speculation: General Pervez Musharraf mused aloud early in 2002 that the al-Qa'ida leader had probably died of kidney failure, because he had taken a dialysis machine into Afghanistan, but would not have been able to use it as a fugitive. But videos smuggled by the network to al-Jazeera TV made it clear that he was all too alive.

While intelligence officers dissect each Bin Laden video or audio tape for clues that might avert further terror attacks, other experts sift them for evidence of his whereabouts and state of health. At various times there have been claims that his appearance showed signs of battle injuries or a minor stroke, though these have come to nothing. But after an American geologist identified the rock strata behind him in an early appearance, and pinpointed a small area of Afghanistan where he thought Bin Laden might be hiding, the al-Qa'ida chief made sure to use a neutral backdrop in subsequent videos.

The last probable sighting of Bin Laden by any Westerner dates back to the final days of the Taliban in late 2001, when special forces and their Afghan allies pursued a "tall man on a horse" into the mountains of Tora Bora. Since then there have been messages from the fugitive at irregular intervals, with some of the gaps so long that speculation of his demise revives, only to dispelled when he surfaces once more. Video footage of Bin Laden has dried up, although al-Qa'ida proved that it has an extensive archive when it marked the fifth anniversary of 9/11 by giving al-Jazeera previously unseen footage of its leader meeting the hijackers in Afghanistan.

IntelCenter, a Washington-based organisation that monitors terrorist communications, said yesterday that the last time it could be sure Bin Laden was alive was on 29 June, when al-Qa'ida released an audiotape in which the terror leader eulogised Abu Musab al-Zarqawi, the former head of al-Qa'ida in Iraq, who was killed earlier that month. It was an unwelcome reminder that however many successes have been scored against the network, its creator remains uncaught. So does his deputy, Ayman al-Zawahiri, and their ally, the Taliban leader Mullah Omar.