Brazilian security forces waged a crackdown Friday on criminal gangs accused of torching vehicles, shooting up buildings and sowing terror in four nights of attacks on dozens of northeastern cities.

One suspect was killed and 17 arrested in the crackdown on the attacks, which authorities say have been organized by jailed gang leaders as a protest against prison conditions and new restrictions on their activities from behind bars.

The security operation targeted gang members in three cities, including Natal, the capital of Rio Grande do Norte state, which has been at the center of the unrest.

According to local media reports, more than 40 cities have been hit by the wave of violence, in which attackers have torched cars, trucks, buses and a health center, and left police cruisers, businesses and government buildings riddled with bullets.

President Luiz Inacio Lula da Silva's government has sent hundreds of federal officers to bolster state security forces.

The number of reinforcements will reach 500 by Saturday, said Rio Grande do Norte Governor Fatima Bezerra.

"We will win this fight, and we will get back to normal," she wrote on Twitter.

In all, three suspects have now been killed in clashes with police and 97 arrested since the violence erupted Tuesday.

Investigators suspect one of Brazil's most powerful organized crime groups, the First Capital Command (PCC), of involvement in the attacks, according to media reports.

Brazil's severely overcrowded prison system is notorious for security failures and corruption that allow crime bosses to continue running their operations from behind bars.

The prison system has a history of deadly riots and clashes between rival gangs.

Rio Grande do Norte's prisons have been hit by allegations of severe abuses, including inmates being tortured and served rotting food.