The authorities in the United States have issued a worldwide alert for a Saudi man suspected of being an associate of the 11 September hijackers.

The Federal Bureau of Investigation (FBI) said it was seeking the immediate arrest of 21-year-old Saud al-Rasheed of Riyadh.

The suspect, described as armed and dangerous, is not thought to be in the United States.

Al-Rasheed's picture was posted on the FBI's website

But in a separate development a man accused of providing fake identification documents to two of the hijackers in the attacks was arrested at Kennedy airport in New York on Tuesday.

Mohamed el-Atriss - a naturalised US citizen of Egyptian origin - was detained by customs officials after his return from Egypt, where he fled last month to avoid arrest.

He is accused of selling fake ID cards to Khalid Almihdhar, who was on the plane that crashed into the Pentagon, and Abdulaziz Alomari, one of militants who boarded the plane that flew into the north tower of the World Trade Center.

The authorities say they are not sure whether Mr Atriss, 43, knew of the hijackers' plans, and federal authorities have not filed any charges against him.

However, he is charged with conspiracy, and manufacturing and distributing fake documents, by authorities in Passaic County in the state of New Jersey.

He will be held without bail pending a court appearance on Friday.

'Armed and dangerous'

The FBI posted a photograph of Mr al-Rasheed on its website, taken from a passport issued in May 2000 and found among pictures of several of the hijackers.

"Law enforcement agencies are requested to stop and detain al-Rasheed and to contact their local FBI office," the FBI statement said. "He is considered armed and dangerous."

The statement added that the alert was issued based on information developed over the last few days from material previously recovered during the war on terrorism.

It is not known how long the government possessed the material.

The FBI has issued several alerts over the year following the attacks but most have been warnings of new terrorist threats rather than wanted notices.