The attack occurred around 12:30 p.m. local time on Tuesday, and witnesses said they heard four explosions and gun fire, according to The Daily Mail, although the reports can't yet be confirmed.
One of the dead is thought to be one of the attackers, who was reportedly around 40 years old. He is believed to have killed himself. The BBC is also reporting that police apprehended another of the grenadiers, but gun fire continues in the area.
The attack took place in Place Saint-Lambert, a busy square in downtown Liege. Around 1,800 buses go through the square daily.