Four people have been killed in a prison in the Brazilian city of Manaus in another round of clashes between rival gangs, BBC reported.

Authorities of the Amazonas state reported that three of the victims at the Vidal Pessoa jail in the city centre were decapitated.

The chaos in Brazil's penitentiary system has left almost 100 inmates killed in the past week in a gang war.

The prison was reopened to house inmates from a jail where 56 prisoners died in a riot last week.

Officials say the prison violence in the state is part of a war between rival gangs over the drug trade.

It has spread to other state prisons; in neighbouring Roraima state, 33 people were killed in clashes on Friday.