BRUSSELS — Authorities have detained some 30 youngsters following scuffles with police and attacks on cars and storefronts in the heart of Brussels, only days after riots left cars ablaze and shops looted.

Belgian Interior Minister Jan Jambon said late Wednesday that action was needed after two such incidents in barely four days. “Behavior like this is unacceptable,” he told VRT network.

The scuffles started in the late afternoon after the arrival of a young French social media star. Some youths smashed windows of shops and cars alike while pelting police officers.

On Saturday night in the wake of Morocco’s qualification for the World Cup, rioters tore up one street in central Brussels and injured 22 officers.

Jambon said the violence fits a pattern and “needs to be countered with tough measures.”