The 90-minute video apparently shows bin Laden, the leader of al-Qaeda, taking part in the planning and preparation of the attacks that killed nearly 3,000 people.

The footage, first aired on Thursday, also shows Abu Hafsa al-Masri, al-Qaeda's then military leader, and Ramzi bin al-Shaiba, co-ordinator of the 9/11 attacks, meeting in al-Qaeda's training camps in Taliban controlled Afghanistan.

The tape also says that a previous unknown Arab Islamist, Abu al-Turab al-Urduni, supervised the training for the attacks.

The video said the preparation for the attacks included not only flight training but also lessons in street-fighting and how to forge official documents.

The video also showed two of the 19 Islamists who took part in the attacks, Saudi nationals  Hamza al-Ramdi and Wael el-Shemari.

The men said that their actions were inspired by an urge to avenge the suffering of Muslims in Bosnia and Chechnya.

Ramzi bin al-Shaiba was captured by the US in 2002. He is now reportedly being held in Guantanamo Bay.

Aljazeera has aired only three minutes of the tape.

Afghanistan training camp

Parts of the tape show bin Laden - wearing a dark robe and white head gear - strolling through an Afghan training camp, greeting dozens of followers, some masked, some barefaced, many carrying automatic weapons.

Aljazeera said that among those he greeted in the footage were several of the 9/11 hijackers but their faces were not clear, and it was not immediately known which ones were shown.

In one scene, bin Laden addresses the camera, calling on all Muslims to support the hijackers.

"I ask you to pray for them and to ask God to make them successful, aim their shots well, set their feet strong and strengthen their hearts," bin Laden said.

The comments were apparently filmed before the attacks but never before released.

The footage also shows scenes of training at the camp.