Two people were seriously injured. A third person, who attempted to intervene, sustained minor injuries to the throat. The attacks happened in two separate incidents, but police believe the same perpetrator was involved.
Homeless people in the neighbourhood are extremely concerned.
Police spokeswoman Marie Verbeke: "We have launched extra patrols in the neighbourhood of the Brussels South Station as a precaution. The other emergency services are aware of the situation too."
The not-for-profit organisation Samu Social that provides aid for the homeless is displaying extra vigilance too.