Fifty-two prison inmates were killed early Monday in northern Brazil when criminal gangs clashed inside a penitentiary, local media reported.
One of the gangs entered an area where members of the other gang were being held in Altamira prison in Para state, website G1 quoted penitentiary authorities as saying.
Fifty-two people were killed, including 16 who were decapitated, reports said. Some of the victims died from suffocation after part of the premises was set on fire.
Two prison guards were taken as hostages, but later released.
Brazil's most recent prison massacre occurred in May, when 55 people were killed in a penitentiary in Amazonas state.
The country's prisons house about 708,000 inmates, nearly 300,000 more than they officially have room for.