At least four inmates were killed on Sunday in a facility in Manaus, the capital of Amazonas state, sending the number of violent prison fatalities over 100 in just one week.
Much of the violence, which includes several massacres with decapitations and disemboweling, has been among rival drug gangs in vastly overcrowded facilities.
On Sunday four inmates were killed in as yet unclear circumstances in a Manaus prison, state public safety officials there said.
Deadly prison riots have intensified in Brazil since a truce broke down in July between the country’s two largest drug gangs, the First Capital Command (PCC) and the Red Command (CV).
The country was hit Friday by a grisly prison massacre at the Monte Cristo Farm Penitentiary (PAMC) in Roraima state that left 31 dead.
That unrest came days after jailed gang members killed 56 rivals in a 17-hour bloodbath at a prison in Manaus.
PAMC, the largest prison in the state, was also hit by deadly violence in October, when fighting between rival gangs killed 10 inmates.
At the time, the prison held 1,400 inmates -- double its capacity.
The states of northern Brazil, which border top cocaine producers Bolivia, Colombia and Peru, are battle zones in the drug trade.
Prisons there -- and throughout Brazil -- are often under the de facto control of drug gangs, whose turf wars on the outside are also fought out among inmates.
Overcrowding exacerbates the problem, activists say.
Brazil’s inmate population has been swollen by efforts to crack down on a violent and lucrative drug trade.
The country’s jails hold 622,000 inmates -- mostly young black men -- according to a 2014 justice ministry report, which found that 50% more capacity was needed.