Hundreds of central African children living in the UK may have suffered abuse or even been killed after being accused of witchcraft, charities say.
Kisanga was convicted of aiding and abetting cruelty
The warning follows the conviction of three people over the torture of an eight-year-old girl.
Four London charities, working with people from central Africa, told BBC News this was not an isolated case.
The children may have been returned to their home countries for "deliverance services" or other punishments.
In one case it was claimed an Angolan child had been sent home two years ago, and had since been killed.
BBC correspondent Angus Crawford said community workers believed the growth of "breakaway churches" could be one possible cause of the abuse.
A minority of these preach a powerful blend of traditional African beliefs and evangelical Christianity.
Community workers also complain of ignorance on the part of the UK authorities, and a lack of resources to tackle the problem.
On Friday three adults were found guilty at the Old Bailey over the torture of an eight-year-old girl in Hackney, east London, after she was accused of witchcraft.
The orphan was beaten, cut and had peppers rubbed in her eyes
The orphan was beaten, cut and had chilli peppers rubbed in her eyes to "beat the devil out of her".
The child's aunt, who cannot be named for legal reasons, was found guilty of child cruelty, while Sita Kisanga and her brother Sebastian Pinto were convicted of aiding and abetting.
The trio, all from London, were found not guilty of conspiracy to murder. They were remanded in custody and the women were warned they faced lengthy jail sentences.
Speaking exclusively to the BBC, Kisanga said the girl was possessed by an evil spirit, known as kindoki.
"In our community, kindoki happens. It is killing people. It is doing bad things," she said.
The orphan was brought to Britain from Angola in 2002 by her 38-year-old aunt after the girl's parents died.
The cruelty started at the beginning of 2003 when a boy told his mother that the girl had been practising witchcraft.
'Today you die'
The child was cut with a knife and beaten with a belt and shoe.
During police interviews, the girl said Kisanga had cornered her in the kitchen and told her "today you die".
The court also heard the girl, now 10, was put into a laundry bag and believed she would be "thrown away" into a river.
Detective Superintendent Chris Bourlet, head of the Metropolitan Child Abuse Command, said such cases were difficult to police: "These are very small churches. Sometimes they meet in very small halls, sometimes in people's houses.
"It's not really the role of the police to go and watch churches."
Mary Marsh, director of the NSPCC, called the case "horrific", saying it had "exposed beliefs held by some in the African community that can lead to child abuse".
Penny Thompson, Hackney Council's Chief Executive, said the case was "very serious".
The City and Hackney Safeguarding Board, which monitors child protection agencies, would be making an independent inquiry.
A new unit called Project Violet had been set up to protect children from abuse as the result of religious or cultural beliefs, police said.