Three people have been shot dead in the Belgian capital Brussels.
Authorities say the incident happened near the Jewish museum in the city.
Emergency services say at least one other person has been seriously injured.
Interior minister Joelle Milquet later told reporters that the gunman apparently parked a car outside before entering the Jewish Museum.
She added the gunman "apparently fired rather quickly, went outside and left".
Brussels mayor Yvan Mayeur said police had a good lead for a suspect, but refused to elaborate.
Belgian foreign minister Didier Reynders, in a post on Twitter, said he was “shocked by the murders committed at the Jewish Museum” this afternoon.
He said he had seen the bodies of the victims.
According to RTBF, a Belgian broadcasting company, a person with a backpack opened fire, then fled.
Mr Reynders, who was in the vicinity, said the scene ``was terrible and left me shocked'' as he saw two of the three dead lying at the entrance of the museum, which is in the touristy Sablon neighbourhood.
The interior ministry confirmed the casualties, adding that investigators were still on the scene gathering details, and that it was too soon to say whether it was an anti-Semitic attack.
However Mr Reynders said 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”.
Police have closed off the area around the museum, near the centre of Brussels, and numerous ambulances were at the scene.
The Sablon area consists of cobblestoned streets with numerous antique shops and museums.
The attack happened during a three-day jazz festival in the neighbourhood, and came on the eve of national and European Parliament elections.
Viviane Teitelbaum, a member of the Brussels parliament, said anti-Semitic attacks reached a peak in the early 1980s but had dropped off before a recent rise in anti-Jewish sentiment.
“It has been a very difficult place to live” for Jews, she said, adding that many young people are leaving the country.
She added that some 40,000 Jews live in Belgium, half of them in Brussels.