A prison brawl in Brazil has left at least 25 people dead after inmates were beheaded and burnt in violent gang clashes.

The bloody battle between opposing factions in the Boa Vista jail began when one wing of the Agricola de Monte Cristo prison broke into another.

Seven of those slaughtered had their heads cut off and six died after being set on fire on Sunday.

Prisoners were armed with knives and wooden clubs in the prison in the capital of Roraima state, news site G1 reported, citing local police.

Around 100 visitors to the prison were held hostage before those involved demanded that a judge come to hear their demands, state Secretary of Justice Uziel Castro said.


Most of the hostages were women.

The prisoners were defeated when special operations police stormed the prison, released the hostages and regained control.

Image: Brazil's prisons are dangerously overcrowded, say activists. File pic

The incident has raised questions about the country's underfunded and overcrowded prison system.

Joana Moura, head of the union of Roraima penal workers, told the Folha de Boa Vista newspaper: "There is no security equipment, there are not enough personnel for the tasks, and the agents are working beyond their limits."

As of the end of 2014, there were 622,000 people imprisoned in Brazil, according to an official report which added that most of the prisoners are black males.

Brazil has the world's fourth largest prison population, the report said, after the United States, China and Russia.

Human Rights groups have long complained about the deplorable conditions in Brazilian prisons.

In late May, 14 inmates died in prisons in the northeastern state of Ceara, which led the Inter-American Commission on Human Rights to issue a statement expressing their concern over prison violence and urged structural reforms.

In a separate incident in September, some 200 inmates rioted and escaped from the overpopulated Jardinopolis prison in Sao Paulo state.

The prison, some 3,400km (2,100 miles) northwest of Rio de Janeiro, is in a state that borders Venezuela and Guyana.