Concern over rise in violence at Durham's Frankland prison
Violence between inmates at the country's largest high security prison has increased, an inspection has found.
Bosses at Durham's high security Frankland prison have been urged to take "prompt action" to tackle a rise in assaults.
The report noted a recent increase in levels of violence involving prisoners.
But inspectors concluded the prison offered a "safe and decent" environment for inmates, many of whom are classed as vulnerable.
The jail holds more than 800 men, many of them Category A inmates.
The report said there had been an increase in assaults on prisoners - up from 11 in the five months to September 2015 to 40 in the five months to February 2016 - some of which were "serious".
It also said there had been one assault on a staff member in the previous six months.
Peter Clarke, Chief Inspector of Prisons, said: "The outcomes for prisoners at Frankland were reasonably good or better. Staff managed considerable ongoing risk every day, while maintaining a safe and respectful regime in which prisoners had good learning opportunities."
Michael Spurr, chief executive of the National Offender Management Service, said: "The prison holds a long-term population including some of the country's most dangerous prisoners, but provides a humane, purposeful environment and manages risk proportionately and effectively.
"The challenges presented by prisoners held at Frankland are considerable but the rehabilitative approach helps provide purpose which helps reduce risk and ultimately protects the public.
"They will continue to build on their successes and build on the recommendations raised in the report."