Prison (illustrative)
Prison (illustrative)Flash90

About 60 people have been killed in a prison riot in Amazon jungle city of Manaus, Brazil, officials said Monday.

The riot was instigated by a feud between rival drug gangs.

Sergio Fontes, the head of security for the Amazonas state, said at a press conference that the death toll could continue to rise as the authorities discover the scale of the violence.

According to Fontes, several of the people killed during the riot were decapitated and that their headless bodies were thrown over the prison wall. Most of the dead were members of a single gang, he added.

"This was another chapter in the silent and ruthless war of drug trafficking," he said.

Pedro Florencio, the Amazonas state prison secretary, called the riot and the ensuing massacre a "revenge killing."

As many as 300 prisoners may have escaped during the carnage, which was said to have been brought under control by 7 AM local time.

Brazil's prison system is notoriously overcrowded and suffer from endemic violence and riots, according to international watchdog organizations. Monday morning's riot was the dealiest Brazil has seen since 1992, when 111 inmates were killed during a rebellion at the Carandiru prison in Sao Paulo state.