US officials say a plot to attack an airliner bound for the US or another Western country with an improved "underwear bomb" has been foiled.
It is reported that authorities in the Middle East seized the device within the last 10 days. Officials in Washington said the plot was detected in its early stages and no US airliner was at risk.
The bomb had design features that were somewhat more sophisticated than a bomb used in two attempted attacks in 2009.
In the first incident, a man equipped with a bomb in his underwear tried to attack a senior Saudi Arabian counter-terrorism official.
The bomber killed himself in the attack but the official survived.
On 25 December 2009, Nigerian-born militant Umar Farouk Abdulmutallab tried to detonate a bomb sewn into his underpants as his flight from the Netherlands to Detroit began its descent.
The device burst into flames but its explosive charge did not detonate.
Abdulmutallab was subdued by fellow passengers and was later jailed by US authorities.
One official said the device seized in the latest investigation used what was supposed to be an improved or redesigned mechanism intended to ensure that the explosive charge detonated.
Like the bombs used in the two previous attempted attacks, the latest device was non-metallic, officials said.
The FBI said in cooperation with security and intelligence partners overseas "an improvised explosive device (IED) designed to carry out a terrorist attack has been seized abroad. The FBI currently has possession of the IED and is conducting technical and forensics analysis on it."
It said initial investigation showed the bomb was similar to devices used by al-Qaeda in the Arabian Peninsula (AQAP) in attempted attacks on planes and in assassination attempts.
US officials said AQAP had also been working to design explosive devices that could be implanted in would-be suicide bombers and there were doctors willing to perform the necessary surgery.
They said implanted bombs were more likely than those built into clothing to defeat airport security though the impact may be weaker.
