BRUSSELS — Belgium launched a nationwide manhunt Sunday for a lone suspect in a shooting spree at the Brussels Jewish Museum that left four people dead.

Deputy prosecutor Ine Van Wymersch said "we call on the whole population to help identify this person." Her office was preparing to publish video taken around the time of the Saturday attack.

She said the gunman who killed an Israeli tourist couple and a French woman on Saturday and left a Belgian in critical condition with shots to the face and throat "probably acted alone, was armed and well prepared." On Sunday afternoon, the injured man who was a receptionist at the museum and in his 20s, died.

Interior Minister Joelle Milquet has said that the shooter parked a car outside before entering the Jewish Museum in the swanky Sablon area of antique dealers, hip cafes and museums, "fired rather quickly, went outside and left."

The museum said in a statement that the gunman came in, started shooting at the tourist couple at the entry "and then went on to the reception where he shot the attendant."

Police had detained one suspect late Saturday but he was soon released and is now considered a witness.

The attack, which came on the eve of national and European Parliament elections, led officials to immediately raise anti-terror measures and protection of Jewish sites.

Van Wymersch said "all options are still open" regarding a motive for the shooting spree. But the government has said it had the hallmarks of an anti-Semitic attack. No one has claimed responsibility for the killings.

On the heels of the Brussels attack, two Jewish brothers wearing traditional clothing were attacked as they left a synagogue in the Paris area late Saturday. One of the brothers was hit in the eye with brass knuckles and is expected to be hospitalized for 10 days, authorities said.

As in Belgium, Interior Minister Bernard Caseneuve ordered police around France to increase security at Jewish houses of worship and other Jewish establishments.

Israeli Prime Minister Benjamin Netanyahu blamed the shooting on European incitement against Israel and criticized what he called "weak condemnation" of anti-Semitic acts.

Netanyahu said at the opening of his weekly Cabinet meeting that "there are those in Europe that are quick to condemn every building of an apartment in Jerusalem, but do not rush to condemn, or condemn with weak condemnations, the murder of Jews here or in Europe itself."

Belgian Prime Minister Elio Di Rupo swiftly condemned the attack and said Belgium stands united with the Jewish community of 40,000.

His office said he also called Netanyahu early Sunday "to express the deep solidarity of Belgium with the Israeli population."

European Jewish Congress President Moshe Kantor planned to meet Di Rupo on Sunday. He said that "attacks on Jewish targets in Europe do not exist in a vacuum, but are part and parcel of an overall climate of hate and incitement against Jewish communities."