SPIN BOLDAK, Afghanistan - Osama bin Laden, if he's alive, celebrated his 50th birthday on Saturday, and his friends in the Taliban prayed for his long life.

Undated picture of the head of the al-Qaeda terror network, Osama bin Laden. The United States faces growing threats on multiple fronts with Al-Qaeda still the top danger, but Iran on the rise and on course to produce nuclear weapons early in the next decade, US intelligence chiefs said Tuesday. [AFP]

The al Qaeda leader's long silence has fuelled speculation that the world's most-wanted fugitive may have died, though many in the international intelligence community reckon Islamist militant Web sites would circulate word of his death.

"He is alive. I am 100 percent sure," Taliban spokesman Mullah Hayatullah Khan told Reuters, adding that senior leaders were in touch with bin Laden, reinforcing a widely held view that he is hiding near the rugged Pakistan-Afghanistan border.

Khan said special prayers were offered by Taliban fighters in camps in Afghanistan to mark bin Laden's birth on March 10, 1957, in the Saudi Arabian city of Jeddah.

"We prayed that Allah may give him 200 years to live," Khan said," by satellite telephone from an undisclosed location.

"When we woke up today, we offered collective and long prayers for him because he is a great mujahid (holy warrior)."

The most recent videotape of bin Laden was released in late 2004 -- subsequent tapes released were identified as old footage -- and around half a dozen audio tapes surfaced in the first half of 2006.

But a long silence since then has fuelled rumours that bin Laden is unwell, or dead, though the United States fears that the al Qaeda network he founded is rebuilding its base in Pakistani tribal lands, and has forged ties with affiliates in Europe, North Africa and the Middle East.

Dead or alive, bin Laden is revered by some as the symbolic leader of a global jihad, or holy war, against the United States, following the September 11, 2001 attacks on New York and Washington that killed more than 3,000 people.

"He is the man who raised voices against excesses being committed on Muslims all over the world," the Taliban spokesman said.

The Taliban were ousted from power by US-backed forces in late 2001 after their leaders refused to surrender bin Laden following the al Qaeda attacks on the United States.

The attacks triggered the largest manhunt in history, with over 12,000 US-led troops scouring the deserts and mountains of Afghanistan for over five years.

The United States also announced a US$25 million reward for any information leading to the arrest or death of bin Laden, but leads on his whereabouts have been few and far between.

Intelligence on the movements of his Egyptian deputy, Ayman al Zawahri, is gathered more frequently.