The man arrested on Friday in the city's district of Laken was identified as Brussels resident Bilal El Makhoukhi, according to the VRT broadcaster.
It still remains unclear what role he played in the terrorist attacks in the Belgian capital.
In 2015, Makhoukhi was sentenced to five years over Sharia4Belgium case (Sharia for Belgium), three of which were suspended. He is said to be a member of a Belgian radical Salafist organization that recruited dozens of volunteers to Syria, spreading its ideology in the Internet and social networks.
On March 22, two suicide blasts ripped through the departure hall of the airport in the northeastern municipality of Zaventem while another explosion hit the Maelbeek metro station near the headquarters of the EU institutions in Brussels, killing over 30 people and injuring at least 300.