Belgian prosecutors say police have detained four people after a series of raids on March 27 in the wake of deadly terrorist bomb attacks in Brussels earlier this week.
Belgium's federal prosecutor's office said in a statement that police had carried out 13 new raids across Brussels and the towns of Duffel and Mechelen to the north "in connection with the terrorism dossier."
It said a total of nine people were questioned, five of whom were later released.
Prosecutors said they could not provide further details.
An investigating judge was to decide later on March 27 whether the four detained individuals will remain in custody.
Belgian prosecutors announced a day earlier that three men arrested in connection with the Brussels bombings have been charged with terrorist offenses.
The attacks on March 22, which were claimed by the Islamic State (IS) extremist group, killed 31 people and wounded some 300 others.
Earlier on March 27, Germany's Die Welt newspaper reported that European security authorities were searching for at least eight more suspects tied to attacks carried out in Paris and Brussels by terrorists affiliated with IS.
The report cited unidentified security sources as saying that the suspects, mainly French and Belgian nationals, are believed to be on the run in Syria or Europe.
Meanwhile, riot police in Brussels on March 27 fired water cannon at far-right soccer fans who descended on a square in the city that has been set up as a shrine to commemorate the victims of the attacks in the Belgian capital.
Hundreds of protesters shouted nationalist and antiimmigrant slogans as they moved in on the Place de la Bourse, where people were gathering to show solidarity with the victims.
White-helmeted riot police used water cannons to push back the crowd, which public broadcaster RTBF described as numbering between 500 and 1,000.