US 'foils terror attack'

Ashcroft praised the CIA and FBI roles in the arrest

The United States authorities say they have thwarted a plot by al-Qaeda to attack the country by detonating a bomb containing radioactive material.

US Attorney General John Ashcroft said a US citizen, Abdullah al-Mujahir, had been arrested on 8 May at Chicago airport after arriving from Pakistan.

I can tell you that we have a man detained who is a threat to the country... thanks to the vigilance of our intelligence-gathering and law enforcement

President Bush

The suspect was alleged to have been planning to build and explode a radioactive "dirty" bomb, which can spread highly toxic material to humans, Mr Ashcroft said.

US President George Bush said Mr Mujahir, previously known as Jose Padilla, was a "threat to the country".

"Thanks to the vigilance of our intelligence-gathering and law enforcement, he is now off the streets, where he should be," he said.

The plot shows al-Qaeda is "alive and active" and will be an enormous boost to the organisation's supporters in the Middle East because it shows they can still attempt to mount operations against the US, says BBC Middle East analyst Frank Gardner.

He adds Western intelligence services believe it is almost inevitable that al-Qaeda will try to mount a second nuclear attack given the relative ease with which radiological materials can be obtained in the US alone.

'Enemy combatant'

Mr Ashcroft said that 31-year-old Mr Mujahir, whom he described as an operative for Osama Bin Laden's al-Qaeda network, posed a serious and continuing threat and was in the custody of the US military.

Abdullah al-Mujahir was jailed in the 1990s

His activities and association with al-Qaeda qualified him as an "enemy combatant", Mr Ashcroft said, adding that there were legal precedents for his detention.

"We know from multiple, independent and closely corroborated sources that Abdullah al-Mujahir was closely associated with al-Qaeda and that as an al-Qaeda operative he was involved in planning future terrorist attacks on innocent American civilians in the United States," the attorney general said.

Mr Ashcroft, who was speaking from Moscow, praised the role of the CIA, FBI and other agencies in the arrest.

The BBC's Emma Simpson in Washington says there has been a spate of warnings in recent weeks of terrorist attacks, and this is just the kind of threat the US authorities had in mind.

Attack at planning stage

Mr Mujahir had been taken to a high security US Navy prison in Charleston, South Carolina, Deputy Defence Secretary Paul Wolfowitz said.

How does a dirty bomb work?

A conventional bomb is packed with radioactive isotopes

The force of the explosion spreads radioactive material over a wide area

Likely to cause radiation sickness in any exposed to the contaminated area

Massive disruption ensues

He said that the suspect's activities had "not gone much past the planning stage", although he displayed some knowledge of the Washington DC area.

Then known as Jose Padilla, Mr Mujahir was in prison in the US in the early 1990s, reportedly for his part in the activities of Chicago street gangs.

He was also put on a year's probation in Florida for aggravated assault and firing a weapon.

He left the country in 1998 after converting to Islam, and visited Afghanistan and Pakistan in 2001.

Zubaydah claim

It was there that he met al-Qaeda officials, Mr Ashcroft said, adding that he "trained with the enemy, including studying how to wire explosive devices".

Bin Laden: May be able to build dirty bombs

Al-Qaeda apparently believed that - as a US citizen - Mr Mujahir would be able to travel freely throughout the country.

In April, Abu Zubaydah, a senior aide to Osama Bin Laden captured by the US, reportedly told interrogators that al-Qaeda had the capability to build a dirty bomb and smuggle it into the US.

Radiological dispersion devices consist of conventional explosives wrapped with radioactive waste which can be found in hospitals and industrial plants.

BBC science correspondent Tom Heap says such materials are much more widely available than weapons-grade material, and are kept in conditions no more secure than the average high street bank.