A 75-year-old woman has died in hospital after being injured in Tuesday's mass-killing in Liege, Belgium, taking the total number of dead to six, including the gunman who killed himself, Belgian news agency Belga reported Thursday.

Apart from the woman and gunman Nordine Amrani, boys aged 15 and 17, a 17-month-old toddler and a cleaning woman also died.

Belgian investigators found the cleaning woman, who appears to have been the first victim, at a warehouse used by Amrani. He killed her before heading for a central Liege square, where he attacked people around a bus station with an assault rifle and grenades.

Another 120 people were injured in the attack, and an additional 40 were treated for shock. Police and the prosecutor's' office in Liege declined to comment Thursday.

(Reporting By Robert-Jan Bartunek)