Five-year-old Utitofong can never go home. She has a loving family and has committed no crime, but her neighbours want her dead. Like thousands of children in the Niger delta of west Africa, she has fallen victim to an outbreak of virulent superstition that sees innocent young people condemned as witches. They can be driven from their villages, tortured or killed.

When her father died, Utitofong was blamed for having caused his death by witchcraft. Her mother spent more than four months' wages on exorcisms, fearing that her daughter would be killed by hostile villagers. But when the money ran out and a pastor proclaimed her a lost cause, Utitofong had to leave home for ever.

There have been Christians in Nigeria since the 19th century. While the majority hold moderate beliefs, an extreme minority has harnessed existing superstitions about black magic and turned them into a lucrative trade. Up to 15,000 children in Nigeria's Akwa Ibom and Cross River states alone have been branded witches by rogue pastors, who charge large sums to "exorcise" them.

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Sam Itauma runs the Child Rights and Rehabilitation Network (CRARN), a makeshift shelter and school in Eket for 150 children who have been deemed to be possessed. The children bear the horrific scars of witch-branding: acid burns, machete wounds and severe malnutrition.

A man from Ibaka in Akwa Ibom, who calls himself "the Bishop", has made a fortune conducting "exorcisms" of children, claiming that they are possessed by the devil and eat human flesh. He told an investigation by Channel 4's Dispatches that he had killed "up to 110 people" who were identified as witches.

Gary Foxcroft, a Briton who is director of Stepping Stones Nigeria, a charity that works with children abandoned because of their supposed "possession", describes the situation as "an absolute scandal".

The distribution of a video claiming to explain how to "diagnose" those possessed is blamed. The film, End of the Wicked, is distributed widely across the Niger delta by the Liberty Gospel Church, a powerful evangelical sect with some 150 branches in the region. Its graphic images of apparently possessed children eating a human carcass, and being inducted into covens, have fuelled an epidemic of paranoia.

But more damaging than this are the film's directions on how to spot a child witch. It tells viewers that an infant under the age of two may be possessed if they scream in the night, experience ill health or get a fever.

Dispatches: Saving Africa's Child Witches, Channel 4, Wednesday 9pm