"They're ultra-fashionable," said Didier Lecourbe, a police officer from the depressed Paris suburb of Aubervilliers. "There are dozens of them. Kids take them out on leads, and even carry baby monkeys around in nappies. But these animals can be very dangerous indeed."

Imported illegally through Spain from Gibraltar, Morocco or Algeria, the Barbary apes are known for their powerful limbs, sharp teeth and short tempers. Veterinary experts say they can be turned into frightening and effective weapons.

"They live naturally on rocks or in a desert environment," said Marie-Claude Bomsel of the natural history museum in Paris. "Removed from their natural habitat, they can become highly aggressive. They bite, and their favoured method of attack is to hurl themselves at people's heads."

Police believe as many as 500 Barbary apes may have been smuggled into France in the past two years. Bought for about £30 each by youngsters visiting their families in north Africa, they change hands on the council estates around Paris for as much as £300.

"Now the authorities have cracked down on pitbulls and the rest, apes look like becoming the new weapon of choice," said Mr Lecourbe. "We've heard of monkey-fights being run in tower block basements."

Ms Bomsel said the museum had received dozens of telephone calls from owners wanting to know how to deal with violent monkeys, or how to get rid of them. "The zoos don't want to know because apes that have grown up outside their natural environment will not live with others," she said. A spokeswoman for the the society for the protection of animals said the society had taken in more than 40 apes in the past 18 months and its Paris animal homes were full.