A Belgian man shot in the attack at the Jewish Museum in Brussels died on Friday, bringing the death toll to four.
Federal prosecutors said the 24-year-old museum worker, who had been in a critical state since the May 24 shooting, died early on Friday afternoon.
An Israeli couple and a French woman were also killed when a gunman opened fire with a Kalashnikov rifle.
French national Mehdi Nemmouche, arrested in the southern city of Marseille on May 30, is suspected of having carried out the attack.
French prosecutors said he was carrying a Kalashnikov, another gun and ammunition similar to that used in the shooting and that he was a repeat-offender who had spent most of 2013 fighting in Syria with Islamist rebels.
Nemmouche, 29, refused to be extradited from France to Belgium during a court hearing on Wednesday. His refusal is likely only to delay rather than block his eventual transfer to Brussels.