"Rough Presentation for Gas Limo Project" describes using limousines to deliver bombs equipped with cylinders of a flammable gas.

The document specifically mentions that limos "blend in" and "can transport larger payloads than sedans ... and do not require special driving skills."

Furthermore, such vehicle could "access underground parking structures that do not accommodate trucks" and "have tinted windows that can hide an improvised explosive device from outside."

Al-Qaida used exploding gas devices in the truck bomb that blew up the U.S. Embassy in Dar es Salaam in 1998 and also in a 2002 attack on a Tunisian synagogue.

Hundreds of limos are expected to swarm over the capital this week, and authorities have warned limo rental agencies to be on the lookout.

Editor's note: