Eight people were killed and at least 10 were wounded in a shooting in the town of Mladenovac, south of Belgrade, local media reported, with police setting up roadblocks in their hunt for the gunman, Trend reports citing Reuters.
Interior Minister Bratislav Gasic described the latest shooting as a "terrorist act", Serbian news portal Telegraf reported, without providing further detail.
According to local media, after a late-night argument in a school yard near Mladenovac, 42 km (26 miles) south of Belgrade, the suspect returned with an assault rifle, opened fire and continued to shoot at people at random from a moving car.
State broadcaster RTS reported a policeman and his sister were among those killed.
Around 600 Serbian police, including elite Special Antiterrorist Unit (SAJ) and Gendarmerie launched a manhunt, dubbed Operation Whirlwind, for a 21-year-old suspect identified only as U.B, RTS reported.