Nine inmates at a prison in the Peruvian capital, Lima, have been killed in a riot that broke out after two prisoners died from Covid-19.
Sixty guards, five police officers and two inmates were injured.
The riot in the Miguel Castro Castro jail is now under control, prison officials said.
There has been a wave of prison unrest linked to fears among inmates over the spread of the virus after more than 600 prisoners were found to be infected.
Thirteen inmates have died of Covid-19, according to Peru's prison authorities.
The riot at Castro Castro started on Monday and was an attempt by the inmates to "facilitate a mass breakout", prison authorities said.
Prison guards called in the police to help quell the unrest. Family members of the inmates alleged that the officers opened fire on the prisoners.
The prison authorities have not released details of how the victims died, but have said their bodies had been taken to a morgue for examination.
Castro Castro houses 5,500 inmates but only has an official capacity of fewer than 2,000 prisoners.
The United Nations High Commissioner for Human Rights, Michelle Bachelet, has urged governments "not to forget those behind bars" during the coronavirus pandemic.
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Peruvian President Martín Vizcarra announced last week that he would grant 3,000 of the most vulnerable prisoners a humanitarian pardon in order to ease prison overcrowding.
Gerson Villar of Peru's National Penitentiary Institute said inmates were clamouring to be included in that pardon.
Protests also took place on Tuesday at Lurigancho prison, Peru's most populous jail with over 10,000 inmates, but ended peacefully after the prisoners came to an agreement with the prison director.
Peru's prison authorities say there have been more than 600 cases of coronavirus inside jails and more than 100 cases among prison employees.