The man convicted of murdering eight-year-old Sarah Payne in West Sussex has been attacked by a fellow inmate in prison, according to sources.
Roy Whiting, 52, was injured in the eye during the assault at Wakefield Prison, in West Yorkshire, on Friday morning.
The Ministry of Justice confirmed an attack took place but said it would not discuss specific cases.
In a statement, the MoJ said the prisoner was treated in the prison's healthcare wing.
"HMP Wakefield manages violent and dangerous prisoners every day and events such as this are rare," it said.
"The bravery and speedy response of staff ensured that this incident was dealt with swiftly and effectively."
A spokesman for West Yorkshire Police confirmed officers were called to an incident involving two prisoners at the jail, at about 0839 BST.
"We were contacted by prison staff who informed us there had been a fight between two prisoners," he said.
"One of the inmates received injuries but they are not thought to be life threatening."
Police said the injured inmate received treatment at the prison, before staff took him to Pinderfields General Hospital in Wakefield for further care.
A force spokesman said no criminal complaints had been made by the injured person, so the incident was not being investigated.
"There was no criminal allegation of assault made to the police so we will not be investigating," he said.
Whiting, a convicted sex offender, was sentenced to life in prison in 2001 for the murder of Sarah Payne, who disappeared while playing near her grandparents' home in Kingston Gorse, West Sussex, in July 2000.
Her body was found in nearby Pulborough 17 days later.
In 2002, Whiting was attacked with a razor blade by fellow Wakefield inmate Rickie Tregaskis.
Last year, a High Court judge reduced Whiting's minimum jail term of 50 years by 10 years.