Three Belgian nationals arrested overnight have been charged with attempting to commit terrorist murder and with taking part in the activities of a terrorist group, Belgium's federal prosecutor said.
Nine other suspects arrested during the overnight searches have been released.
The 12 were arrested across Belgium overnight after police carried out about 40 house searches in the country, the federal prosecutor's office said in a statement earlier.
Europe is on high alert as the Euro 2016 soccer tournament is under way in neighbouring France.
Islamist suicide bombers killed 32 people in Brussels in March following attacks in Paris in November in which 130 people died.
Investigators have confirmed links between the perpetrators, some of whom were based in Belgium.
Flemish public broadcaster VTM said the people arrested overnight were suspected of planning an attack in Brussels this weekend during Belgium's soccer match with the Republic of Ireland.
Belgian police on Wednesday received an anti-terror alert warning that a group of so-called Islamic State fighters recently left Syria en route for Europe planning attacks in Belgium and France, security officials said.
Yesterday police arrested and detained a man named as Youssef E.A, a Belgian national, on suspicion of taking part in terrorist activities in connection with the Brussels attacks.
