If you, as a man, are particularly attached to your penis, then you might want to avoid going to the Congo where sorcerers are reportedly stealing and shrinking people's penises.

The police in Congo have had to arrest 13 suspected sorcerers accused of using black magic to steal or shrink men's penises to prevent attempted lynchings triggered by the fear of the alleged witchcraft.

These reports, while sounding bizzare to most westeners, are not uncommon in West Africa, where ritual killings to obtain blood or body parts still occur and belief in witchcraft is still widespread.

It something akin to the alien invasion panic of October 30, 1938 in the US, rumours of penis theft started to circulate last week in Kinshasa and the air waves were saturated with discussions advising listeners to beware of fellow passengers in communal taxis wearing gold rings.

Some of the alleged victims claimed that sorcerers simply touched them to make their genitals shrink or disappear.

"You just have to be accused of that, and people come after you. We've had a number of attempted lynchings. ... You see them covered in marks after being beaten," said Kinshasa's police chief, Jean-Dieudonne Oleko.

Police arrested the accused sorcerers and their victims in an effort to avoid the sort of bloodshed seen in Ghana a decade ago, when 12 suspected penis snatchers were beaten to death by angry mobs. The 27 men have since been released.

"I'm tempted to say it's one huge joke," Oleko said.

"But when you try to tell the victims that their penises are still there, they tell you that it's become tiny or that they've become impotent. To that I tell them, 'How do you know if you haven't gone home and tried it'," he said.

Some of the residents in Kinshasa have accused a separatist sect from nearby Bas-Congo province of being behind the witchcraft in revenge for a recent government crackdown on its members.

"It's real. Just yesterday here, there was a man who was a victim. We saw. What was left was tiny," said 29-year-old Alain Kalala, who sells phone credits near a Kinshasa police station.