New York: An al-Qaida videotape, obtained by CNN, shows a level of sophistication in bomb making that would allow terrorists to arrive in a target city unarmed and put together explosive devices using common household materials.

The tape, parts of which were aired by CNN on August 22, is essentially a training video for al-Qaida recruits. It shows an instructor giving step-by-step lessons on how to make TNT and build detonators and fuses using easy-to-obtain materials.

"Let me mention that this nitric is locally made," the instructor says as he carefully pours chemicals into a glass bowl to make a compound used in detonators. "Mix the whole thing together until the liquidation process is over."

Tony Villa, a consultant for the US government on terror tactics and bomb making, said the video confirms his fear that al-Qaida's techniques are now so sophisticated that its bomb makers can cheat detection.

"The overarching point here is that they can pick any venue or target city – with nothing on them – arrive in that city and, based on what we are seeing here, (construct a bomb) using common materials," Villa said.

The training video is among 64 al-Qaida tapes CNN obtained, nearly all of which pre- date the September 11 terror attacks, from a source in Afghanistan who said they were found in a house where al-Qaida leader Osama bin Laden had stayed. The network said it had paid $ 30,000 for the footage.

The August 22 broadcast was the fourth instalment of a series CNN is airing from August 19. Earlier instalments showed al-Qaida recruits conducting poison gas experiments on dogs, training in terror techniques and Laden warning of a missive against Americans.

PTI