The arrest came during a terror raid in the northeastern part of Brussels. The country has been on high alert since a terrorism attack earlier in the year.
The man, in his mid-thirties and known only by the initials A.B., was detained after police found weapons in the raid, which was conducted on Monday in Brussels' Schaerbeek neighborhood.
The city's public prosecutor said on Tuesday the search "was aimed at a person suspected of being in possession of arms and explosives and who was thought to have made threats of a terrorist nature."
The suspect, who is expected to face a judge on Tuesday, was already known to authorities for committing acts of theft and assault.
Police also seized computer equipment in the raid. Further details concerning the suspect were being withheld from the public.
Belgian authorities have been conducting frequent raids across the country since a home-grown terrorist attack in the capital on March 22 left 32 civilians dead. Despite heightened security, there have also been several terrorism-related incidents since then, including a stabbing attack in Schaerbeek in October.
That same month, authorities charged four people with involvement in terrorism after raiding 15 homes in the cities of Ghent, Antwerp and Deinze.
Some of the perpetrators of the March attacks also took part in the terrorist attacks in Paris the previous year that left 130 people dead.
Arrest in Austria
Also on Tuesday, police in Austria arrested a 25-year-old Moroccan asylum seeker suspected of plotting a terror attack in Salzburg. While police said they had found no suspicious materials in the refugee center where the man was living, they are not ruling out terrorism just yet.
Authorities said the man is suspected of "belonging to a terrorist organization," though they didn't offer any specifics.
The police began their investigation last month after being tipped off about a possible attack.
blc/rc (dpa, AP)