A gunman shot dead two police officers and a bystander in the eastern city of Liege, according to reports in Belgium.
Two other people are said to have been wounded in the incident.
State broadcaster RTBF said the shooting happened on Tuesday near a cafe on the Boulevard d’Avroy.
The gunman fled the scene, taking a cleaning woman hostage at a nearby school, but he was later “neutralised”, RTBF reported, quoting police and fire services.
There was no immediate indication that the incident was terror-related.
Video posted on Twitter by a person claiming to be a witness showed people running in the area. About six gunshots could be heard.
Belgian police and military have been on alert since suicide bombers killed 32 people at the Brussels airport and subway system in 2016.
An official in the Belgian city later told The Associated Press that a gunman has killed three people.
The official confirmed that the attacker had also been killed.
Michel Firket, from Liege City Hall, said that “beyond the attacker, who was shot, there are three dead – two police officials and a passer-by”.