The attacks and fire-bombings sweeping in Brazil's northeastern state of Ceara continue unabated despite the deployment of at least 300 members the elite, military-style National Police Force to help bring an end to the violence.

The state's public security department said that buses and cars were torched and gas stations were attacked on Sunday in Fortaleza, the capital, and in at least six other cities.

Police killed two suspects in a shootout. More than 100 people have been taken into custody since the violence that broke out on Wednesday.

Authorities have said the attacks were ordered by organized crime groups in retaliation for plans to impose tighter controls in the state's prisons. Brazil's prison gangs are powerful and their reach extends outside the country's penitentiaries