French jihadist Salah Abdeslam, already jailed for his role in the 2015 Paris attacks, refused to take the stand Monday on the first day of the trial for the 2016 suicide bombings in Brussels.

"The way in which you are treating us is unfair," the 32-year-old told the presiding judge, leaving the dock a few minutes after the start of the first hearing in a trial due to last at least eight months.

Nine alleged members of the Islamic State (IS) group cell that launched both the March 2016 suicide bombings in Belgium and the November 2015 attacks in Paris face terrorism charges.

The Belgian attacks, in which three suicide bombers hit Brussels airport and a crowded underground metro station, killed 32 people and shattered the lives of hundreds of wounded or traumatised survivors.

A tenth suspect, presumed killed while fighting in Syria, will be tried in absentia.

The trial is the largest ever staged in front of a Belgian jury, with 960 civil plaintiffs represented and the sprawling former headquarters of the NATO military alliance converted into a high-security court complex.

After Monday's preliminary hearing, the court will sit again on October 10 to choose 12 jurors and 24 potential substitutes. Evidential hearings will begin on October 13 and last at least until June next year.