Several cities in north east Brazil are suffering from serious unrest caused by marauding criminal gangs.
For the third night, gang members set buses ablaze and carried out gun attacks on buildings in urban areas in Rio Grande do Norte state.
The attacks are thought to have been sparked by conditions in jails holding gang members.
Brazil's government sent hundreds of federal security forces to the region earlier this week.
Justice and Security Minister Flavio Dino said hundreds more could be sent in the coming days as unrest continues. The state government has convened a crisis cabinet and has asked the federal government for more support.
The attacks were ordered from within the state's jails when gang members' requests for televisions, electricity and conjugal visits were turned down, Brazilian news outlet Terra quoted the state's secretary of public security Francisco Araujo as saying.
Conditions in Brazil's notoriously overcrowded jails have long been under scrutiny.
In 2017, the government sent a Penitentiary Intervention Task Force (FTIP) to Rio Grande do Norte jails following a riot which left at least 30 inmates dead. Some have said the task force routinely uses violent methods to bring prisons under its control.
Local media have reported that two rival gang factions have now struck a temporary truce and become allies in the attacks against security forces.
Several cities in Rio Grande do Norte have suspended public transport and closed schools in the wake of the violence.
At least two people were killed in clashes with police earlier in the week and 67 people have been arrested, reported AFP.
Across the region, police have also seized a number of firearms, explosive devices and vehicles, as well as drugs and money.