Keychain guns

Designed to fire gas cylinders, these tiny Bulgarian-made weapons can also fire .32 caliber bullets. Once the arming ring is locked, the buttons on top of the device can fire one round from each of its two barrels.

At just one inch wide and three inches long, they are easily concealable and will not set off most airport metal detectors.

Because of their small size and short barrel, the devices have a great deal of recoil, are extremely loud and are not very accurate. They are described by some experts as a "last resort" weapon.

Since the end of the Cold War, these weapons have become readily available in southern Europe for as little as $20, Interpol officials say. The FAA issued a warning in May for airports to be on the lookout for the "keychain guns."