Abdullah Mehsud, who Pakistani officials say is dead, was a Taleban veteran of Guantanamo Bay who became one of Pakistan's most wanted Islamic militant leaders.
Mehsud said he led his fighters by taking risks
Mehsud, 33, spent 25 months in custody at the US base in Cuba before his release in March 2004.
He commanded militants who kidnapped two Chinese engineers in Pakistan's South Waziristan region shortly after his release.
One of the Chinese men was killed during a rescue bid by Pakistani forces.
As a young man, Mehsud fought for the Taleban against the Northern Alliance in Afghanistan.
He lost a leg in a landmine explosion a few days before the Taleban took Kabul in September 1996.
He surrendered along with several thousand fighters to the forces of Uzbek warlord, Abdul Rashid Dostum, in December 2001 in Kunduz, northern Afghanistan, and was later turned over to the US military authorities.
Mehsud studied at a government college in Peshawar before attending a seminary where he befriended Afghan Taleban members and joined their movement.
Mehsud, whose real name is Noor Alam, is a Pashtun, the same ethnic group as the Taleban and belongs to the Mehsud tribe that inhabits South Waziristan on the Afghanistan border.
Mehsud declared holy war on President Musharraf
The BBC's Rahimullah Yusufzai in Peshawar says his long hair and daredevil nature made him a colourful character.
After his return from Guantanamo, Mehsud became a hero to anti-US fighters active in both Afghanistan and Pakistan.
He was a comrade of another tribal militant commander, Nek Mohammad, who was killed by a Pakistani army missile in June.
Our correspondent says Mehsud sometimes rode a camel or horse while visiting his fighters in the mountains.
On other occasions, his men drive him in a vehicle and protected him round-the-clock.
In a telephone interview with the BBC in 2004, Mehsud told our correspondent that he led his fighters by example by taking risks and surviving in tough conditions.
Criticising US policies toward Muslims, he said the American occupation of Iraq and Afghanistan was a provocation for the followers of Islam and must be avenged.
He said he did not want to fight the Pakistan army but had declared jihad, or holy war, against the government of President Pervez Musharraf, who he accused of carrying out US policies in the region.