Khalid Sheikh Mohammed
Khalid Sheikh MohammedReuters

The man accused of masterminding the September 11 2001 Al Qaeda attacks on the US has released a document renouncing the use of violence to spread Islam.

The surprising change of heart is contained in a wider "manifesto" released by Khalid Sheikh Mohammed from his cell in Guantanamo Bay, Cuba. The 36-page document was Mohammed's first public communication since 2009, when he was formally charged with terror offenses.

"Don't believe the media that the Mujahideen believe that Islam spread in the past and will prevail in the future with the sword... the holy Koran forbids us to use force as a means of converting!" the arch-terrorist wrote, according the Huffington Post, which first published the document.

Those words stood in sharp contrast to both his past words and actions, as well as those of the "mujahideen" in question. The mastermind of the 9/11 attacks, which killed 2,976 people, is also believed to have been behind a string of other terrorist atrocities, including the Bali Nightclub Bombing in 2002 and the kidnapping and murder of US journalist Daniel Pearl - he even claimed to have personally beheaded Pearl with "my blessed right hand".

Even after his arrest in 2006, he told a US military commission that "it would have been the greatest religious duty to fight you over your infidelity". 

Yet now, Mohammed says he pursues more "peaceful" modes of proselytizing, attempting to persuade his captors to convert to Islam.

"It is my religious duty in dealing with any non-Muslims such as the people in the court (the judge, the prosecution, attorneys, etc.) to invite them to embrace Islam," he wrote. "I realize very well that you have heard about Islam and know much about it. But it is my own belief that Allah will ask me on the Day of Judgment why I did not invite these people to Islam?"

Despite apparently renouncing violence, Mohammed - who says he is "very happy" in prison - also used the opportunity to rail against the west in general and America in particular, and appears convinced that the western world is collapsing around his jail cell.

Mohammed, turns 50 this year, faces the death penalty if found guilty of charges relating to his part in the 9/11 attacks.