A former US sergeant has been secretly charged with allegedly helping Saudi exile, Osama Bin Laden, carry out attacks on Americans.

The New York Times has given an intriguing account about how American investigators are tracking down the dissident Saudi millionaire and his followers.

The Americans blame them for a series of attacks against Americans, including the embassy bombings in East Africa, an attack in Saudi Arabia and the explosion at the World Trade Centre in New York.

The former American Special Forces sergeant Ali Mohammed is said to have once trained Islamic militants in New York to fight the Russians in Afghanistan.

People who were at a particular refugee centre in Brooklyn are alleged to have been responsible for some of the subsequent anti-American plots.

Charges unknown

It is said Ali Mohammed also once trained fighters at a guerrilla base in Afghanistan which was recently bombed by the Americans after the embassy attacks.

Born in Egypt, he left the American Special Forces in 1989. He was known there for being a devout Muslim.

He was was charged last month although the charges against him are not known. He is being held in a prison in New York.

The investigators are also trying to reach a deal with one of his former associates who was arrested near Washington this year.