The attack took place near a school in Liege, which is about 60 miles east of Brussels.
Officials said the attacker stabbed officers, stole their guns and opened fire on the officers. He also killed a 22-year-old passenger when he opened fire on a car nearby.
Police later shot and killed the gunman. He had earlier fled to a nearby college and taken a female hostage. No students at the college were harmed, and the gunman was flushed out of the building.
Sources told ABC News that the suspect was Benjamin Herman, a Belgian national who police knew to have been radicalized in prison.
The Belgium federal prosecutor's office told ABC News that "there are elements that make us believe that it was a terror attack."
ABC News contributed to this report.