Washington: Airports all over the world have been asked by the US Homeland Security to be on the lookout for suspicious stuffed items among luggage after US intelligence concluded that al-Qaida operatives are being trained to conceal 'nitrocellulose' bombs inside them.

Intelligence officials have confiscated al-Qaida manuals and picked up several indications that the terror network is attempting to create a chemical called nitrocellulose to fashion explosive devices that could be smuggled aboard jetliners, media reports said.

"We judge this type of threat to be real and continuing. We have received reports from several credible, independent sources that al-Qaida is training to build such bombs," the Homeland officials were quoted by 'Washington Post' as saying.

Among other things, confiscated al-Qaida training manuals show the sophistication of its preparations, they said.

Explosives experts said that the detonating power of a nitrocellulose bomb depends on numerous factors--but most particularly on how tightly cotton-like material is packed.

Producing such explosives, said Gregory G Baur, a former director of the International Association of Bomb Technicians and Investigators, "requires somebody who has some sophistication and who knows what he is doing".

Items such as buttons, zippers or wristwatches could be used in tandem with tightly packed nitrocellulose as power sources or ignition components to set off a detonation, the directive said.

PTI