Gang violence hits at least 28 cities, including Natal, provincial capital of Rio Grande do Norte state, officials say.
Gang members have torched cars, shot up public buildings and sowed terror in a wave of predawn attacks on numerous cities in northeastern Brazil that has now lasted two nights, authorities said.
On Wednesday, officials said the attacks in the state of Rio Grande do Norte, which began late on Monday, were planned from inside prison by gang leaders as a protest against jail conditions and retaliation for new regulations cracking down on criminal factions' operations within the penal system.
At least 28 cities have been hit by the violence, including the state capital, Natal.
At least two suspects were killed in clashes with police, according to news website G1.
Two other people were wounded, and 30 arrested, it said.
Police said one of those killed was Jose Wilson da Silva Filho, 29, the leader of the state's largest organised crime group.
"He was responsible for financing and distributing weapons to the group that carried out the attacks," they said in a statement.
Public Security Minister Flavio Dino said on Twitter that President Luiz Inacio Lula da Silva's government had deployed 220 federal officers to reinforce state security forces, and was prepared to increase the deployment "to whatever number is necessary."
"The state is standing strong and working … to restore normality to the people of Rio Grande do Norte. All necessary measures are under way," Governor Fatima Bezerra told journalists.
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'Inhumane and degrading' conditions
Local media carried footage of cars, trucks and buses in flames, and of police vehicles, businesses and government buildings riddled with bullets.
Brazil's independent prisons inspector, MNPCT, found in a report last year that conditions in Rio Grande do Norte's jails were "inhuman and degrading."
It also identified cases of inmates being tortured and served rotting food, according to G1.
The governor vowed a "deep investigation" of those claims.
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.
It has also been hit by numerous deadly riots and clashes between rival gangs.
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