RIO DE JANEIRO — A heavily armed group of bank robbers wreaked havoc across a southeastern Brazilian city early Monday, striking several banks, setting fire to vehicles and tying hostages to their getaway cars, in an assault that left at least three people dead, officials say.

Even in a country long accustomed to random spasms of violence, Brazilians reacted with shock and fear.

The group stormed Araçatuba, a city of 200,000 in São Paulo state, around midnight to rob several banks. Gunshots punctured the early-morning quiet. Authorities asked residents to stay inside.

Images on social media and local news reports showed at least 10 people clinging to getaway cars, apparently strapped there to deter fire from police.

The feeling was one of “helplessness,” Mayor Dilador Borges told Rádio CBN. It was a “night of terror.”

Little information has been released about the three people who were killed. Local media outlets reported that two were residents and one was a member of the criminal group. The hostages were reportedly released after the group escaped.

The raid bore the characteristics of a new, elaborate form of crime in Brazil: shock-and-awe bank heists. The nighttime raids are intricately planned, well choreographed, and executed by well-financed groups equipped with the weaponry and gadgetry of war.

The group flew a drone over Araçatuba during Monday’s raid, according to local reports, to track movements throughout the city. People who were still out in the city square were taken as hostages. Members of the group set fire to a large vehicle to block police from following them. Residents said the group left behind explosive devices throughout the city.

“I’m in tears and desperate,” one person in Araçatuba wrote on Twitter. “Help, Lord, protect the people here. My God, it looks like a movie scene what is happening here.”

No arrests have been reported.

Such attacks, orchestrated by what are thought to be specialized criminal groups, often follow a similar pattern. They occur at night, often in midsize cities, usually around the end or the beginning of the month, when banks are more likely to be filled with cash to pay out people waiting for public benefits.

In November, in the city of Araraquara in São Paulo state, a criminal group set fire to multiple vehicles around a police station to block a response while they robbed several banks.

Weeks later, in the city of Criciúma in southern Santa Catarina state, at least 30 heavily armed members of a criminal group in 10 vehicles attacked a military police station and struck Banco do Brasil in what authorities called the largest robbery in state history.

In the city of Cametá in the northern state of Pará, a group took hostages, shot into the air and used explosives during another bank heist.

Jânia Perla Diógenes de Aquino, a criminologist at the Universidade Federal do Ceará, said the bank robberies have grown increasingly sophisticated as financial institutions have adopted more methods to stop them.

“It’s what is customary to call among police and some journalists the ‘new banditry,’ ” she said last year in an interview with Folha de São Paulo newspaper. “With these new groups, you have, instead of trying to avoid a confrontation with the police, an attempt to provoke one.”

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