Late on Thursday, a man with an automatic weapon went on the attack. He is said to have traveled in a vehicle, reports the state television station RTS.
The perpetrator has not yet been caught and a police hunt is underway for him.
Interior Minister Bratislav Gašić calls the incident a “terrorist act”.
The mass shooting in Mladenovac comes a day after a teenager shot dead eight classmates and a guard at a school in Belgrade.
The text is updated