On Wednesday morning 8 properties were searched in Ternat (Flemish Brabant), the Antwerp district of Borgerhout and the centre of Antwerp.
Although no weapons or explosives were found, four people were taken away for questioning. Two have since been released, albeit with an electronic tag, while the other two have been detained.
The four are believed to have been involved in the recruitment of jihadi on behalf of the terrorist group IS. Some of them are also believed to have been intending to go to Syria themselves. The initial investigation also points to them having been planning an attack somewhere in Belgium.
No link has yet been found between the four and the terrorists that were involved in the attacks on 22 March in Brussels and Zaventem.