A woman stabbed and wounded three people on a bus in Brussels and was then shot and wounded by police, the public prosecutor's office for the Belgian capital said.

Officials were not immediately available for comment but public broadcaster RTBF quoted unidentified sources as saying police did not believe the incident was politically motivated and that the assailant had mental health problems.

The local prosecutor's office was handling the matter, not the federal body which deals with cases of suspected terrorism.

The Belgian capital has been on high alert since local Islamic State militants carried out the attacks in Paris last November and suicide bombings in Brussels itself in March.

Since a man killed 85 people in Nice last month by driving a truck into Bastille Day crowds, a string of less violent incidents elsewhere on the continent has kept Europeans on edge.