RIO DE JANEIRO—Armed robbers hit several banks in a small Brazilian city on Monday, using locals as human shields, leaving a trail of explosive devices, and shooting at police in an assault that killed at least three people, a senior state security official said. The brazen attack around midnight in Araçatuba, a city of roughly 200,000 people in the interior of Sao Paulo state, is the latest in a series of increasingly violent recent bank heists in Brazil. More than 20 heavily armed men carried out the attack, using 10 cars, Alvaro Camilo, the executive secretary of Sao Paulo’s military police, said at a news conference. As the criminals made their getaway, they used locals as human shields, and burned cars, while leaving a trail of explosive booby traps across the city, the military police said in a statement. The attackers used drones to monitor the streets as they entered the …