Belgian police raided homes in Brussels on Tuesday and detained 10 people linked to a recruiting network for the Islamic State group in Syria and Iraq.
“Our investigation points to several persons having left for Syria to join Islamic State,” Belgium’s federal prosecutors said in a statement.
Nine raids were carried out in four suburbs, including the Molenbeek neighborhood where many extremists have stayed.
The statement said the police action has helped “to establish that several people have probably gone to Syria to join Islamic State.”
Prosecutors said they had seized computer equipment and mobile phones and they are currently being examined.
A judge is due to decide later on Tuesday whether those detained should be charged.
The raids are not linked to the deadly attacks in Paris last year.
Belgium has one of the highest per capita rates of participation in militant groups such as Islamic State in Syria and Iraq.
According to figures from the International Centre for the Study of Radicalisation, Belgium has supplied 40 fighters per million inhabitants to fighting in Syria and Iraq – more than any other European country. Denmark comes a distant second place, with 27 fighters per million.
More than one quarter of the population of Brussels, the “EU’s capital”, is Muslim, mostly first and second generation Moroccans and Turks.