Al-Qaeda terrorists have threatened to unleash a "nuclear hellstorm" on the West if their leader and world's most wanted terrorist Osama bin Laden is nabbed.

A senior al-Qaeda commander has claimed that the terror group has stashed away a nuclear bomb in Europe which will be detonated if bin Laden is ever caught or assassinated, according to new top secret files made public by internet whistleblower WikiLeaks.

The documents are secret details of the background to the capture of each of the 780 people held at or have passed through the Guantanamo Bay detention camp in Cuba, along with their medical condition and the information they have provided during interrogations.

The documents have been released to select European and US news outlets and reveal that the day 9/11 terror killings took place in United States, the core of al-Qaeda was concentrated in a single city of Karachi in Pakistan.

The intellectual author of September 11 attacks watched the horrifying scenes of the planes crashing into the twin towers of World Trade Centre beamed live on TV with key al-Qaeda commanders at a safe house in Karachi.

While in a nearby hospital, the accused mastermind of the bombing of USS's Cole off Yemen waters was recovering from an tonsillectomy, the alleged organiser of the 2002 Bali bombing was buying lab equipment for a biological weapons programme.

Within a day much of the al-Qaeda leadership disappeared back to Afghanistan to plan for a long war, the Washington Post reported quoting the fresh leaks on whereabouts of the international al-Qaeda terror brigade.

The cache of classified military documents portray the planning of the 9/11 terror attacks and whereabouts of its plotters including the world's most wanted terrorist Osama Bin Laden and his deputy Ayman al-Zawahiri on that fateful day.

The Guantanamo detainees are assessed "high or medium or low" in terms of their intelligence value and the threat they pose while in detention and the continued threat they might pose if released.

The leaks say that four days after September 11 attacks, bin Laden visited a guest house in Afghanistan's Kanadhar province where he told his gathered Arab fighters to "defend Afghanistan against infidel invaders" and to "fight in the name of Allah".

The intelligence report says after the 9/11 attacks began a peripatetic three weeks for bin Laden and his deputy as they criss-crossed Afghanistan handing out assignments to followers, meetings with top Taliban leadership and delegating control of al-Qaeda to the group's 'shura' council, presumably because he feared being captured or killed as US forces closed in.

The leaks also refer to a meeting held close to Afghan capital Kabul's guest house where bin Laden gave instructions to continue operations against Western targets, dispersed his fighters from training camps and send women and children including, some of his wives to flee to Pakistan.

The tapes also refer to a meeting in October 2001 between bin Laden and Taliban leader Jallaudin Haqqani, who continues to lead a deadly insurgency against the US and its allies in Afghanistan.

It was only after dispersing his fighters and handing the reins of his dreaded organisation to 'shura' council that bin Laden and Zawahiri fled to the cave complex in Tora Bora near Jalalabad where he was last seen giving a speech to his close followers on November 25.

The Guantanamo leaks have a trace of bin Laden till the Tora Bora caves and according to US intelligence, the al-Qaeda chief is known to have survived intense US air strikes on the caves and escaped the dragnet of American special forces sent to hunt him down.

WikiLeaks said that bin Laden and his deputy Zawahiri separated from Tora Bora, while the latter is supposed to have taken refuge with an Afghan family, little is known about the whereabouts of the world's most wanted man.

According to the new documents, in December al-Qaeda top lieutenants gathered at Zarmat, in mountainous regions of Afghanistan between Kabul and Khost, where they began to plan new attacks until they were finally captured.

Among those who met at Zarmat were Khalid Sheikh Mohammad, the self-described mastermind of 9/11 attacks, Abd al-Rahim al-Nashiri, the alleged planner of the USS Cole attack and Abu Faraj al-Libbi, a key facilitator for bin Laden.

They were addressed by bin Laden at a gathering which was teeming with fighters who were waiting for al-Qaeda to return their passports so they could flee across the border to Pakistan.

After the Zarmat conclave, Mohammad and other senior al-Qaeda fighters began their return to Karachi.

Gradually, Mohammad and other operatives were picked up by Pakistanis working with CIA and FBI. Ramzai Binalshibh, a key liaison between September 11 hijackers was arrested at a safe house in Karachi on the first anniversary of the attacks.