He was blown up in the caves of Tora Bora. He was on dialysis and dying of kidney disease. He was in the hands of Pakistani intelligence and about to be turned over to the United States. Rumors of Usama bin Laden's death or capture go back years, and they have always proved greatly exaggerated.

The latest came Saturday, when a leaked French intelligence document citing a "usually reliable" source said the Saudi secret service was convinced the 52-year-old Al Qaeda terror chief had died of typhoid last month in Pakistan.

Officials from Riyadh to Paris to Washington rushed to insist they had nothing to substantiate the report, but not before news of it reached every corner of the globe and renewed the debate about why the world's largest dragnet has failed to get its man.

"There has been a grave failure five years after 9/11 that the true leaders of the attacks are still free, and that they are still alive," said Rohan Gunaratna, head of terrorism research at Singapore's Institute of Defense and Strategic Studies.

Gunaratna cited comments by bin Laden's no. 2, Ayman al-Zawahiri, released on the fifth anniversary of the attacks, as evidence the French report was erroneous.

"Ayman al-Zawahiri issued a statement on Sept. 11 in which he specifically refers to Usama bin Laden being alive," Gunaratna says. "There is no reason for al-Zawahiri to lie, since he wants to keep his credibility within the movement."

A Pakistani counterterrorism official with intimate knowledge of the hunt also dismissed the French report, saying nothing was known about bin Laden's health or location. He spoke on condition of anonymity, citing the sensitivity of the matter.

The denial was echoed by a purported spokesman for the Taliban, the former Afghan regime that sheltered bin Laden after the 9/11 attacks. He also asked not to be named.

The French report is not the first to allude to bin Laden suffering from a life-threatening illness.

For years, intelligence services took seriously assessments that bin Laden might be suffering from kidney disease, and there were even reports he was forced to lug a dialysis machine from one mountain hideout to another.

But in 2003, Amer Aziz, bin Laden's former doctor in Afghanistan, shot down the reports. He told The Associated Press he gave bin Laden a complete physical in 1999, and saw him again in November 2001 while he was on the run from U.S. forces, and found no sign of illness on either occasion.

"If you are on dialysis, you have a special look. I didn't see any of that," Aziz told a reporter at his office in Lahore, Pakistan following his release from U.S. custody.

The latest video featuring fresh footage of bin Laden came out in 2004, just before the U.S. presidential elections. In it he appeared healthy and relaxed, particularly for a man who was believed to be hiding in the rugged mountains between Pakistan and Afghanistan, or possibly in Afghanistan itself, in the remote, forested eastern province of Nuristan.

The U.S. has conducted hundreds of search-and-seizure operations in the region but has been stonewalled by an increasingly unfriendly local population.

A number of audiotapes of the terror leader have come out since the 2004 video, the latest in June, and a video that featured what appears to be older footage of bin Laden was released in September.

The lack of film of the terror chief since 2004 has further muddied the waters. His decision to appear only on tape could be his way of heightening his mystique, or denying his pursuers visuals that might reveal his whereabouts. Or it could be an effort to hide his state of health.

Paul Wilkinson of the Centre for the Study of Terrorism and Political Violence at the University of St. Andrews in Scotland said the latest report of bin Laden's death could prompt his inner circle to advise him to deliver proof he is alive and healthy.

He speculated that the French report may have been leaked to shake the branches and illicit just such a response from the terror leader, giving the intelligence community a chance to home in on "chatter" among terrorists.

"It does create psychological pressure on the people and operatives" close to bin Laden, Wilkinson said. "There will be an expectation that he make some sort of appearance."

The years of false hope and genuine close calls have contributed to the aura that bin Laden enjoys among his followers. They have also added to the frustration of those charged with bringing him to justice.

In 1998, following the bombing of two U.S. embassies in Africa, the U.S. launched 62 Tomahawk cruise missiles at two al-Qaeda training camps in Afghanistan. It was believed bin Laden was at one of them meeting with several of his top men, but left shortly before the missiles struck.

Following the Sept. 11 attacks and the fall of the Taliban, Afghan militiamen fighting on behalf of the United States felt certain they had surrounded bin Laden at Tora Bora.

Villagers reported seeing him hike into the mountains, and accounts of devastating airstrikes on the caves prompted rumors that bin Laden was dead.

He wasn't.

In the end, one of the Afghan warlords the United States was relying on for ground operations betrayed the others, Afghan fighters told the Associated Press, and bin Laden escaped into Pakistan.

In 2003, Pakistani forces raided the village of Lattaka, near the border with Afghanistan, on intelligence that bin Laden might be hiding there. In 2004, U.S. Lt. Gen. David Barno said from Afghanistan that he expected to bring bin Laden to justice that year, and Pakistani intelligence officials described him as being boxed in, but he was never captured.

Since then, the trail of the world's most wanted man has gone cold, but that hasn't stopped the rumors.

An Iranian state-run radio station sparked worldwide headlines in February 2004 when it flashed an urgent story that bin Laden was in the hands of Pakistan's intelligence agency. The source of the report turned out to be a Pakistani journalist at a newspaper in the western city of Peshawar, who claimed to have been misquoted.

A 2005 posting on an Islamic Web site that began with a headline saying bin Laden was dead also turned out to be false, but not before the news sent world stock markets briefly soaring.

Reports that bin Laden has been nabbed were even used in a computer virus attack, when thousands of messages were posted on Internet chat sites in 2004 that began with the subject line "Usama bin Laden captured." When users clicked a link that was supposed to take them to photos, they triggered the virus.