Four people believed killed and two wardens taken hostage in disturbances at Cascavel state penitentiary in Parana state

This article is more than 6 years old

This article is more than 6 years old

Rioting prisoners in Brazil have decapitated two inmates and are using their severed heads to threaten two prison wardens they have taken hostage.

At least four people are thought to have died in disturbances at the Cascavel state penitentiary in Parana state, which has highlighted the brutal conditions inside the country's prisons.

According to the authorities, about 700 inmates have taken part in the uprising, which began on Sunday morning when two guards were taken captive while they were serving breakfast.

The prisoners then ran amok, storming other areas of the facility and climbing on to the roof where – wearing balaclavas – they burned mattresses and ran up the flag of the First Capital Command criminal organisation.

Two prisoners were beheaded and two thrown off the roof.

The rebels are demanding an end to strip-searches and shackles, a relaxation of visiting arrangements, better food and more dialogue with the authorities over how the facility is run.

"They are using the severed head of one of the prisoners to inflict psychological torture on one of the hostages," Jairo Ferreira, lawyer for the prison agents' union, told the Gazeta do Povo newspaper. "There are scenes of terror inside the jail now."

Gang leaders often hold court in Brazil's prison system. Earlier this year authorities in the northern state of Maranhão released mobile phone footage of three bodies that were decapitated during a riot at the Pedrinhas prison last December. In 2013 at least 60 inmates were killed there – often during clashes between rival gangs.

Police and guards have also been responsible for much of the bloodshed, most notoriously in São Paulo's Carandiru prison in 1992, when military police stormed the building and killed 102 inmates after a battle between gang members in which nine others died.

Human rights groups also cite cases of rape, torture and chronic overcrowding.

The UN high commissioner for human rights, the Inter-America Commission on Human Rights, Amnesty, Human Rights Watch and other groups have repeatedly expressed concern about the dire conditions faced by Brazil's prison population, which has almost quadrupled in the past 20 years to more than half a million inmates.