The US attorney in Manhattan said the men had connections with Osama bin Laden, the leading suspect in the bombings who features on the FBI's Most Wanted list.

One of the defendants, Ayman al-Zawahiri Zawahiri, is described in the attorney's indictment as part of the leadership of Mr bin Laden's organisation, al-Qaeda.

He is said to be the leader of al-Jihad in Egypt, which is dedicated to overthrowing the Egyptian Government.

Osama Bin Laden: denies involvement with bombings

He is alleged to have sat on the consulting council which planned the embassy attacks and is thought to be with Osama bin Laden in Afghanistan.

Six months before the bombings, the two men endorsed an Islamic "fatwah" sanctioning the killing of Americans. Mr Zawahiri faces a possible death sentence if convicted.

The second new defendant, Khaled al-Fawwaz, is said to have set up businesses in Nairobi with al-Qaeda's military commander.

Mr Fawwaz, who is in custody in Britain, is alleged to have set up a media information office in London in 1994 to provide cover for al-Qaeda's military activities.

A hearing is to be held on 24 June to decide whether Mr Fawwaz should be extradited to the US. He faces a maximum sentence of life in jail without parole.

The embassy bombings killed more than 250 people, including 12 Americans.

The revised indictment adds 29 new counts to the previous conspiracy, murder and weapons charges, and brings the total number of defendants to 15.