Five men accused of plotting the deadly September 11, 2001 attacks have been formally charged with crimes including murder and terrorism in a chaotic marathon hearing.

Five men accused of plotting the deadly September 11, 2001 attacks have been formally charged with crimes including murder and terrorism in a chaotic marathon hearing.

The supposed 9/11 mastermind Khalid Sheikh Mohammed and the four other accused defered their pleas at Saturday's proceedings in a military tribunal at the US naval base in Guantanamo Bay, Cuba -- which lasted more than 13 hours.

In addition to Mohammed, Ali Abd al-Aziz Ali of Pakistan, Mustapha al-Hawsawi of Saudi Arabia, Ramzi Binalshibh of Yemen and Walid bin Attash of Yemen face the death penalty if convicted for their roles in the attack in which planes were hijacked and used to strike New York, Washington and Shanksville, Pennsylvania.

The defendants were charged with "conspiracy, attacking civilians, murder and violation of the law of war, destruction, hijacking and terrorism" in connection with the attacks, the most lethal on US soil in modern history.

The five men have been held for years at the US naval base in southeastern Cuba while a legal and political battle has played out over how and where to prosecute them. Debates have also raged over their treatment.

Mohammed was arrested in 2003 and spent three years in secret CIA jails where he was subjected to harsh interrogation techniques including waterboarding, which rights groups denounce as torture.