An "angelic looking boy" aged 12 has been identified as at severe risk of being lured into violent Islamist extremism, a senior police officer revealed today.

The white schoolboy is the youngest of 124 children and youths, mainly Asian teenagers from Muslim backgrounds, who have been earmarked by police forces for close-contact work to try and stop them being groomed for terrorism.

The child was brought into a police station in West Yorkshire by a headmaster who said he was unable to cope with his behaviour.

Sir Norman Bettison, chief constable of West Yorkshire, said the boy's family was cooperating fully with police and other agencies trying to help him.

"He is at risk of being a violent young man and a threat to society," said Sir Norman. "He is not a Muslim, he is not driven by ideology - he's too young to spell the word - but he is being influenced and intoxicated by the imagery and appeal of jihadist and other internet violence."

Sir Norman shocked a conference of chief police officers by showing them a picture of the boy. Although his face was obscured, he was seen to be a small-framed child with tousled blond hair.

The boy came to Britain with his family in 2005 fleeing "a despotic regime" and seeking asylum, he said.

His behaviour led to him being referred to social services within a year of his arrival. He had been involved in assaults and criminal damage at his school and, after police were asked to intervene, they found videos of beheadings on his mobile phone.

The boy had downloaded the footage from jihadi websites and was sharing it with classmates. He spoke of wanting to become a sniper and asked questions about what it would be like to kill someone. His father had turned a collection of imitation guns which fired ball-bearings into police.

Inquiries into the 12-year-old's past revealed that he had been accused overseas of helping two other boys rape his five-year-old sister.

Sir Norman added: "This case presents real challenges and complexities. He seems addicted to violence."

The police approach to the boy, and other youths, was to regard them as vulnerable people rather than criminals.

Sir Norman said that discussions about jihad and the ideology of al-Qaeda were common in internet chatrooms and on social networking sites while schoolchildren were being targeted for indoctrination by street-corner radicalisers.

Trying to prevent that grooming process was an essential part of the Government's counter-terrorism strategy, he said.

Sir Norman said: "The success of the UK effort to counter the Al-Qaeda threat has pushed back the supply chain of sophisticated explosive material, attack planning and training for would be terrorists. Like any determined, ideologically based terror group, core AQ are prepared to wait for opportunities to strike.

"In the meantime, the AQ brand of violent extremism continues to spread like a virus, infecting young minds. The internet, the radicaliser and the disaffected peddle the virus.

"We know there is a latent sense of grievance in the minds of many young people which, with the right conditions, can lead to the desire for violent expresson.

"What happens if they learn how to build and deploy an explosive device that will cause mass casualties, or if core AQ can get their hands on these people to act as mules for a more sophisticated attack."

The scheme to identify vulnerable youths is being piloted in London, Lancashire and West Yorkshire before being extended to other parts of the country. Sir Norman said it relied heavily on co-operation with Muslim communities.

He added: "Every young Muslim will be exposed to a conversation about al-Qaeda. In the same way that we urge parents to talk to children about drugs or knives, I would say to Muslim parents: 'Talk to your kids about the dangers of being influenced by the message of violent struggle'."

Assistant Commissioner Bob Quick of Scotland Yard said at the conference, in Liverpool, that despite an apparent lull in terrorist activity the threat was still present.

He added: "There is no reason to drop our guard one iota. There's nothing to lead us to believe we're immune from the events we've seen over the last four summers."

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