An attack on a Brussels Jewish museum has claimed a fourth victim, with Belgian police hunting the gunman releasing chilling video footage of the shooting.
An Israeli tourist couple and two museum staff - a French woman and a Belgian man - died from gunshots to the face and neck after a man fired inside the museum on Saturday afternoon before escaping on foot.
The Israelis and the French woman, who worked as a volunteer, died on scene. The Belgian, in his 20s and employed at the museum's reception, was rushed to hospital critically injured and died on Sunday afternoon.
The first such attack in more than 30 years in Belgium has revived fears of a return of anti-Semitism, with Israeli premier Benjamin Netanyahu lashing out at Europe's "hypocrisy" towards the Jewish state.
Speaking on arrival in Israel, Pope Francis said on Sunday he was deeply saddened by the killings.
"My thoughts go out to those who lost their lives in the attack in Brussels," he said.
"I entrust the victims to God."
Appealing to the public for help in finding the shooter, deputy public prosecutor Ine Van Wymersch said he "probably" acted alone and was "well prepared and well armed".
Police released three videos of the suspect - in sunglasses, a cap and blue shirt - walking into the museum with two bags, removing an automatic rifle, shooting through a door, and then walking away again.
Van Wymersch said as yet there was no claim for the shooting.
"I cannot confirm that it is a terrorist or anti-Semitic act" but "all leads remain open", he added.
French President Francois Hollande, who along with Netanyahu had a phone conversation with the Belgian premier, said he had no doubt about the "anti-Semitic character" of the attack.
Netanyahu, welcoming Pope Francis in the Holy Land, hailed the pontiff for his "determined stance against anti-Semitism, especially in light of the growing hatred of Jews that we are witness to in these days."
The attack in the busy heart of Brussels, minutes from a packed streetside jazz festival, came as the country headed into a crucial general election held alongside a vote for the European parliament.
"An election day is usually a celebration of democracy. Today it is clouded," said Belgium's Prime Minister Elio Di Rupo. "It is on everyone's mind.
"In Belgium we are not accustomed to such acts of barbarity."
About 40,000 Jews live in Belgium, roughly half in Brussels and the remainder in the port city of Antwerp.
Condemning the "terrible act" in the city which hosts EU and NATO headquarters, European Commission president said: "This was an attack at European values which we cannot tolerate."
Flowers and candles were laid out in front of the museum on Sunday as mourners trickled by to pay respects.
The government was beefing up protection with 24/7 police protection at schools, synagogues and cultural centres in line with a decision to place Jewish institutions under maximum security.
"These measures will remain in place for now," a government statement said.
There was no security at the museum leading up to the attack and Jewish community leaders said there had been no threats.
Police late Saturday detained and interrogated a person thought to have driven the gunman to the scene.
He said he was there but denied involvement and was released.