The attack, which left three dead and one seriously injured, happened at the Jewish Museum in Brussels on Saturday.

Belgian Prime Minister Elio Di Rupo said he was "very shocked" by the attack and that "all Belgians are united" as he voiced his support for the Jewish community.

It came on the eve of elections in Belgium for a new federal government as well as for its regional parliaments and the European Parliament.

Foreign Minister Didier Reynders was in the area at the time of the fatal shooting and said the scene "was terrible and left me shocked" as he saw two of the victims lying outside the museum in the city's Sablon neighborhood.

"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," he said.

Interior Minister Joelle Milquet told reporters that the suspect apparently parked a car outside before entering the Jewish Museum.

Milquet said anti-terror measures were immediately heightened following the incident.

Mayor of Brussels Yvan Mayeur also said the police had a good lead for a suspect, but refused to comment further.

In a statement, European Jewish Congress President Moshe Kantor said that, even though it had yet to be established whether the attack was anti-Semitic, "we are acutely aware of the permanent threat to Jewish targets in Belgium and across the whole of Europe."

French President Francois Hollande condemned the "horrifying killings with the greatest force."

In a statement, he expressed France's solidarity with neighboring Belgium and condolences to the families of the victims.

lw/tj (AP, AFP)