Furthermore, Belgium's radical Islamic scene has provided a support structure for French extremists, who have traditionally skipped the border to evade surveillance at home. They are also more able to blend in thanks to the shared language, Otto said. However, with a greater focus on intelligence-sharing in the wake of the Paris attacks, that could change.
Benyaich stressed that extremists comprise a very small proportion of the Muslim community in Belgium, but warned that lawmakers should launch a comprehensive strategy to tackle radicalization while the problem is relatively manageable. This would require cooperation with social services, education, the judicial system and police force, as well as a realistic foreign policy, he said.
"We need a paradigm shift," Benyaich said. "If they wait too long, if the situation in Middle East deteriorates, it will be even worse."