In Bulgaria a remodelled gas-spray gun costs up to 200 leva (102 euros) and can be sold in Spain, Holland, Greece, or Turkey for up to 800 euros for a profit of 800 percent, said Vladimir Gaidarski, a police expert in arms trafficking.

A survey by the Bulgarian Centre for the Study of Democracy (CSD) and the British group Safer World, published Wednesday, stated that these illegal arms workshops were concentrated in central Bulgaria, near the town of Kazanlak, home to two major arms manufacturing companies, VMZ and Arsenal.

Many workers at these two arms companies lost their jobs after the fall of communism in 1989.

The remodelling of a gas pistol into one which fires bullets only requires the replacement of the barrel. CSD's survey among VMZ and Arsenal management has indeed proven that "the most commonly smuggled component was the barrel".

Another weak point in manufacturing process was said to be "the discarding of defective parts that can still be used to make a low-quality firearm."