Khalid Sheikh Mohammed, the reputed mastermind of the September 11 attacks, told a military judge at his arraignment Thursday that he welcomes the death penalty as a way to martyrdom and ridiculed the proceedings as an "inquisition".

In his first public appearance since his capture five years ago, Mohammed wore dark-framed prison-issue glasses, a turban and a bushy, gray beard, and was noticeably thinner – a stark change from the slovenly man with disheveled hair, unshaven face and T-shirt from the widely distributed photograph after his seizure in Pakistan.

In this image reviewed by the US Military, observers are escorted by US troopers toward the entrance to the war crimes courthouse at Camp Justic, the legal complex of the US Military Commissions, at Guantanamo Bay US Naval Base, Cuba, Thursday, June 5, 2008. The accused mastermind of the September 11 attacks and four alleged confederates faced a military judge in their long-awaited first appearance before a war-crimes tribunal. [Agencies]

He and four other detainees accused of plotting al-Qaida's 2001 attack were at turns cordial and defiant at their arraignment, the first US attempt to try in court those believed to be directly responsible for killing 2,973 people in the bloodiest terrorist attack ever on US soil. All five said they did not want attorneys and would represent themselves.

Their war-crimes tribunal is the highest-profile test yet of the military's tribunal system, which faces an uncertain future. It also threatens to expose harsh interrogation techniques used on the men, who were in CIA custody before being transferred to Guantanamo in 2006.