Brazil prison violence leaves at least 18 inmates dead with some burned alive and beheaded

The incident is thought to be reflection on the poor prison conditions in the country

Inmates use mirrors to view visitors from their cells in a Brazil prison (Getty Images)

At least 18 people have been killed, with some burned alive and beheaded, in violence at two Brazilian jails, authorities have said.

Around 100 relatives of the inmates, mostly women, were taken hostage during one of the riots, which was sparked by rifts between two rival criminal factions at the Agricola de Monte Cristo prison in the Roraima state capital, Boa Vista, officials said.

The clash between two rival gangs killed 10 on Sunday, regional government spokeswoman Jessica Laurie told AFP.

"The inmates were armed with stones and pieces of wood that they ripped from the walls. They used those bits of wood to decapitate their rivals. It was very brutal," she said.

"Seven bodies were found burned and three others beheaded."

The confrontation has been blamed on members of the Primeiro Comando da Capital faction invading a prison wing where inmates from the Comando Vermelho faction were held. The two groups are some of Brazil's biggest gangs.

Prisons nationwide have been on alert since the rival gangs declared war, Roraima state Justice Secretary Uziel Castro said.

But guards were caught by surprise on Sunday because the riot broke out during visiting hours - a traditional time of truce, he added.

Local media reported that 25 inmates had been killed in the violence on Sunday.

Another riot broke out on Monday at a prison in the northwestern state of Rondonia, officials said.

"A group of inmates blocked their rivals in their cell and set it on fire. We suspect a clash between rival factions," a police official in the state capital, Porto Velho, said.

"There are thought to be eight people dead, but the bodies are burned and the medical authorities will have to confirm" the toll, a police spokesman said.

The incident "is a reflection of the lack of interest from the state government" in the prison system, the head of the union of Roraima penal workers, Joana Moura, told the Folha de Boa Vista newspaper.

"There is no security equipment, there is not enough personnel for the tasks, and the prison officers are working beyond their capacity," he said.

Some 622,000 people were imprisoned in Brazil as of the end of 2014, according to a Ministry of Justice report, which added that most of the prisoners are black males.

That makes it the world's fourth-largest prison population, the report said, after the United States, China and Russia.

Additional reporting by agencies