Three people were killed and one badly injured in a shoot-out on Saturday in Belgium.
A Jewish community figure, Joel Rubinfeld, told AFP it clearly "is a terrorist act" as a man had been seen driving up and entering the museum before opening fire inside and running off. According to RTBF, a Belgian broadcasting company, a person with a backpack opened fire then fled.
Mr Rubinfeld, who heads the country's anti-Semitic League, said the act was the result of "a climate of hate."
Didier Reynders, Belgian foreign minister, said on Twitter: "I am shocked by the murders committed at the Jewish museum, I am thinking of the victims I saw there and their families."
He added that "you cannot help to think that when we see a Jewish museum, you think of an anti-Semitic act. But the investigation will have to show the causes."