It was not known if that incident was linked to Wednesday's raids on addresses in Antwerp and its suburbs, the nearby village of Kasterlee and the city of Ghent.
Belgian authorities have stepped up their surveillance of extreme-right suspects since the country was rocked by the case of radicalised soldier, Jurgen Conings, last year.
Conings sparked a month-long manhunt after he went missing with military weapons and threatened to target state officials and a high-profile virologist.
His body was later found in a forest after he shot himself dead.
