9/11: The World Trade Center south tower burst into flames
The World Trade Center south tower (L) burst into flames Reuters

The trial of Khalid Shaikh Mohammed and four others, all accused in 9/11 terror attacks, is set to begin in 2021, the 20th anniversary of the incident that shook the entire world, reports said.

According to The New York Times, a military judge on Friday set the date of January 11, 2021 for the death penalty trial of the five accused. They're set to be tried at Camp Justice, the war court compound at the Navy base in Guantánamo Bay.

The five face charges with plotting the worst terror attack in the US that led to the country's involvement in a long war against terrorism in many countries, including Afghanistan and Pakistan.

Mohammed has been described as the architect of the plot in which 19 men hijacked four commercial passenger planes and slammed two of them into the World Trade Centre towers and one into Pentagon. The twin attacks killed 2,976 people.

The fourth, believed to be aimed for the Capitol, crashed into a Pennsylvania field instead.

The four others — Walid bin Attash, Randi bin al-Shibh, Ammar al-Baluchi, and Mohammed's nephew Mustafa al-Hawsawi — are accused of helping the hijackers with training, travel, and finances.

Mohammed was also included in the 1998 bombings of US embassies in Kenya and Tanzania, and the 2000 attack on the US Navy warship the USS Cole.

Mohammed and others, who were captured in 2002 and 2003 in Pakistan, were held in a secret prison network of black sites by the CIA. They were tortured by US authorities with waterboarding, sleep deprivation and other physical as well as mental abuse before being sent to Guantánamo in 2006.

Their trial was delayed because of former President Barack Obama administration's plan to try the five men in federal court in New York City, but protests and then legislation in Congress prevented him from doing that.

The September 11, 2011 attack, carried out under the leadership of al-Qaeda founder Osama bin Laden, was the most devastating strike on American soil in modern times.

The fallout of the attack made bin Laden the most hunted man in the world. He was killed in a firefight with US forces in Pakistan in 2011, almost a decade after the deadly incident.