Belgian authorities have stepped up security at the country's Jewish sites after three people were shot dead at a Jewish Museum in Brussels.
A fourth victim remains in a critical condition.
Police said a man who had been detained after the May 24 attack was released without charge.
A manhunt was launched for another suspect.
Two of the dead were Israeli tourists.
The Belgian prosecutor's office said the victims were struck by bullets in the face or throat.
Prime Minister Elio Di Rupo expressed support for the Jewish community.
Israeli Prime Minister Benjamin Netanyahu strongly condemned the killings, saying they were, "the result of endless incitement against the Jews and their state."
The incident took place as Belgians go to the polls for national and European parliament elections on May 25.
Based on reporting by Reuters, AP, and dpa