Al-Qaida's alleged former media director wrote letters from Guantanamo acknowledging he typed the wills of two Sept 11 hijackers and pledging to continue "jihad by word and pen," according to evidence in the Guantanamo war crimes tribunal on Tuesday.

Yemeni captive Ali Hamza al Bahlul is on trial at the Guantanamo Bay US naval base in Cuba, where a jury of nine US military officers will have to decide whether creating propaganda is a war crime.

Prosecutors allege Bahlul was Osama bin Laden's media secretary and part of the Al-Qaida leader's trusted inner circle. They accused him of scripting the videotaped wills of Sept 11 hijackers Mohamed Atta and Ziad al Jarrah, who were his roommates in Kandahar, Afghanistan, in 1999.