German police say a man arrested after the biggest DNA test in the country's history has confessed to the sexual abuse and murder of an eleven-year-old girl.

He was among fifteen-thousand men in north-western Germany who submitted to saliva tests voluntarily after the attack in March.

His sample matched genetic material left on a knife at the scene of the crime.

He admitted the crime -- and a similar rape two years earlier -- immediately after he was arrested.

The man is said to be an unemployed father-of-three, but police have not released his identity.

Correspondents say large-scale DNA testing is only used occasionally and the German operation followed a public outcry over several recent murders of teenage girls.