Criminal gangs in Brazil have set fire to four buses and attacked a police station in the north-eastern city of Sao Luis, authorities say.
They say the order for the attack came from gang leaders arrested at the notorious Pedrinhas penitentiary, where at least 59 inmates died last year.
"The attacks are in reaction to recent measures to curb jail violence," said the Maranhao state government.
A six-year-old girl who was inside one of the buses suffered severe burns.
"Her mother asked the criminals not to harm the children, but they showed no mercy and set fire to the girl," a relative told O Globo newspaper.
Four other people were injured in the attacks, which took place on Friday night in the outskirts of Sao Luis.
A police station was also attacked, with several shots fired from a passing car.
Eight suspects have been arrested, said Maranhao state Security Secretary Aluisio Mendes.
Extra troops had been deployed across the city, he added.
Local gangs were blamed for similar attacks in the Maranhao state capital earlier last year.
The authorities have linked the latest wave of violence to a recent report compiled by the federal government.
The report by a judge highlighted violence inside the Pedrinhas penitentiary and put pressure on the state government to act, correspondents say.
Video taken inside the prison also shows the torture of one inmate at the hands of others - and cases of beheadings.
Extra policemen have since been deployed inside Pedrinhas. But on Thursday two more bodies were found at the penitentiary.
Brazil has the world's fourth-largest prison population, with half a million inmates occupying spaces for 300,000.