12 arrests as Belgium swoops on terror suspects
Those detained on Friday night are suspected of plotting a terrorist attack, prosecutors said on Saturday.
They were among 40 taken in for questioning, BBC reported.
Searches were conducted in 16 municipalities, mainly around Brussels, with checks on 152 lock-up garages.
On March 22, bombs killed 32 people at Brussels Airport in Zaventem, and one at Maalbeek metro station in the capital city.