At least five inmates have died and 18 have been injured during an armed riot in Peru's largest prison.
The prison is overcrowded, with more than 8,000 inmates
The country's prison chief said the flare-up in violence was due to turf wars between rival gangs in the jail.
He admitted that guns and firearms circulated freely inside the prison, and that gangs ran a trade in commodities such as food and alcohol.
More than 8,000 inmates are crammed into the Lurigancho prison, east of the capital, intended to house under 2,000.
The body of at least one inmate was lowered over the prison wall.
"Firearms enter the prison from various sources: negligence, corruption or because of inadequate security at the entrances," Wilfredo Pedraza, head of the country's prisons, told local radio.
"It is a reality that I'm not going to hide."
Mr Pedraza said that after firing tear gas to disperse the inmates, riot police had moved into the prison but were still coming up against pockets of resistance.