One of the two men convicted as children of killing toddler James Bulger in one of the country's most notorious murders is back in prison after breaking the rules governing his release, authorities said on Tuesday.

Jon Venables, who was 10 when he and a friend took the two-year-old from a shopping mall before torturing him and beating him to death by a railway line, was jailed for a minimum of eight years in 1993.

Venables, 27, was returned to custody following an undisclosed breach of the conditions surrounding his release in 2001 "on licence," a system where offenders are allowed out of prison as long as they follow certain rules.

"We can confirm that Jon Venables has been recalled to custody following a breach of licence conditions," the justice ministry said in a statement.

"Offenders on licence are subject to strict conditions. If they breach those conditions they are subject to immediate recall."

A justice ministry spokesman would not say what rules Venables had broken or give any more details.

Typical rules govern where an offender can live, whom they are allowed to contact and what sort of treatment or counselling they must undergo.

Anyone recalled to prison must go before a parole board before they can be freed again.

Little official information has been released about Venables or his accomplice Robert Thompson. Strict court orders prevent the media from identifying the pair or saying where they live and what they do.

Denise Fergus, the mother of the murdered toddler, has campaigned for the pair's relative anonymity to be lifted.

The murder shocked Britain and was widely reported around the world. A security camera still showing the killers leading the toddler away from the shopping centre in Liverpool became a haunting image of the case.