The explosion occurred on the street in front of the synagogue on Monday night, Liège police announced. It caused material damage to the synagogue and blew out windows in buildings across the street.
Police are initially investigating what caused the explosion. The city's mayor says it was a clear anti-Semitic crime.
The area has been cordoned off and the federal police's anti-terror unit has been called into the case, according to RTBF.
