The arrests last month, which came after a tip-off from terrified residents that the six were allegedly hawking human body parts, turned the spotlight on the darkest of South African practices.

The police are convinced that the body parts were to be sold to a sangoma — a traditional healer — to make muti, meaning medicine. Some Africans believe that muti made with human body parts is the most potent of all.

The four men and two women made a pre-trial appearance yesterday. During two previous court appearances hundreds of people demonstrated outside the court, threatening to kill the accused if they were released on bail. All six are now being held in police cells for fear they would be murdered by fellow inmates if they were kept in the local Grootvlei prison.

Abel Tubane, a protester outraged that the six are accused of committing murder to make money from selling body parts, said: “You can sell oranges or apples to earn a living.”

Thandi Gulwa, another protester, was enraged that the accused could insult African traditions in such a way. “We use herbs to be cured, not human flesh,” she said.

But although muti killing is a taboo subject, the Bloemfontein case is far from being an isolated incident. Two men and a woman recently appeared in Khayekutsha Magistrates’ Court, outside Cape Town, charged with killing a baby and frying her intestines to make muti to help them to find a job.

At about the same time, a young woman’s head was found floating in a Johannesburg reservoir, fuelling speculation that she had been killed for her body parts. Last year police arrested a man after he was caught trying to sell a head for £900 for use in traditional medicine.

The South African police force boasts the world’s only specialised muti murder investigation force. Gerard Labuschagne, who is in charge of it, believes that as many as 300 such murders are committed every year.

“Apart from a handful of high-profile cases, most muti murders go unreported,” Dr Labuschagne said. “They happen in South Africa fairly regularly, at least once a month. But for many police officers they are nothing unusual. They are just treated as another murder, so there are a lot of muti-related killings out there that never come to our attention.”

Nor are they restricted to South Africa. In 2001 the torso of a boy was found in the Thames in London. Police arrested 21 people as part of the investigation into what they believe was a ritual killing.

For centuries herbs, roots, powders, tree bark, skins and animal entrails have been the stock in trade of Africa’s traditional healers.

Dismissed as “backward and primitive” during the colonial and apartheid eras, African traditional medicine is undergoing something of a renaissance with Western scientists eager to examine traditional herbal remedies in their quest for new drugs.

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