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More than 80 children have suffered appalling abuse after being branded as witches in a crimewave fuelled by medieval beliefs imported from Africa, Asia and the Caribbean.

The scale of the problem - with many youngsters being beaten, starved and kept in cages - was revealed as a football coach was found guilty of torturing a boy to death.

Eric Bikubi, 28, faces life in prison after murdering 15-year-old Kristy Bamu in a four-day orgy of almost unimaginable violence.

Over the last decade, Scotland Yard has recorded 83 cases of children suffering barbaric treatment including bizarre exorcism rituals. But detectives fear there may be hundreds of other young victims.

Bikubi was in the grip of a lifetime obsession with kindoki, or witchcraft, and believed he had special powers to detect evil. His girlfriend, former Marks & Spencer worker Magalie Bamu, 29, the victim’s eldest sister, was also convicted of murder at the Old Bailey.

Kristy suffered 130 injuries as he was attacked with weapons including a metal bar, hammer, chisel, pliers and even heavy ceramic floor tiles.

He drowned in a bath on Christmas Day 2010 in front of his four terrified siblings as Bikubi hosed them down with freezing water in an abhorrent “cleansing” ritual.

The murder took place just nine days after a woman disembowelled her four-year-old daughter as a sacrifice because she believed the child was possessed.

Shayma Ali, who was later detained indefinitely in a mental hospital, was obsessed with evil spirits and had removed all the eyes from the little girl’s toys.

Both cases, which took place just a few miles apart in East London, shocked detectives. They warned the number of cases linked to witchcraft is growing but the beliefs behind them remain little understood.

Officials suspect grotesque acts continue to thrive behind closed doors, fuelled by a toxic combination of extreme evangelical Christianity and traditional beliefs.

In some of the most serious cases police suspect children may have been sent to their native countries where they face torture, sexual abuse and even murder.

Scotland Yard is overhauling its specialist religious and cultural abuse unit, Project Violet, to better focus on the dark practices. Senior officers are worried the abuse has slipped down the agenda since the death of eight-year-old Victoria Climbie in 2000 at the hands of her aunt who branded her a witch.

Detective Superintendent Terry Sharpe, said the crimes were almost certainly ‘far more prevalent’ than official figures suggest. He said: ‘Children have been physically beaten and forced to drink unknown liquids in rituals to rid them of evil spirits. They have been starved or deprived of sleep. They have had liquids poured on their genitals and been murdered.’

Kristy was killed as a Christmas trip with his two sisters and two brothers, aged between 11 and 22, from their home in Paris, descended into a nightmare.

The siblings stayed at an eighth-floor council flat in Forest Hill, East London, which Bikubi and Bamu had recently occupied.

The horror for the family began when Bikubi unleashed a prolonged attack after Kristy wet himself, an act linked by some to witchcraft.

The heavily-built sportsman accused the teenager of trying to control another child in the house and of orchestrating a series of unlucky events.

He punched, kicked and headbutted his victim before beating him with a metal weight-lifting bar ‘as hard as he could’ and knocking out his teeth with a hammer. In one act of savage cruelty, as his siblings were hit, forced to join in and help clear the blood, Bamu ripped apart one of his ears with a pair of pliers.

Five hours of desperate phone calls were made to Kristy’s parents in Paris but at first they did not believe their children and were then unable to travel because of the Christmas break.

On Christmas Day, with his face beaten to a barely recognisable pulp, Kristy was thrown into a bath. His last words were ‘I just want to die now’ before slipping underneath the water.

Bikubi, an unemployed failed football agent, said his “battle against witchcraft” began in earnest when he travelled to Britain to escape civil war in his native Congo aged seven or eight. His defence team argued he was suffering a mental disorder, but an expert told the court he was “calm, lucid and rational” when he murdered Kristy.

Speaking after the trial, the victim’s father said Bikubi showed less compassion to his son than a butcher would show a cow in an abattoir. Mr Bamu said: ‘I had so much pain in my heart that I can’t express it, this pain.’

Bikubi and Bamu will be sentenced on Monday. - Daily Mail