The 23 suspects face charges linked to attempted terrorist attacks and the assassination of Afghan anti-Taliban commander Ahmad Shah Massood in 2001.
Former professional footballer Nizar Trabulsi, is the only person to have pleaded guilty in the case.
He admitted to having plotted an attack on the Kleine Brogel army base in north-east Belgium where US troops are stationed.
Prosecutors are demanding 10-year jail term for Trabulsi, and are seeking between 18 months and 10 years for the co-accused.
According to court documents, Trabulsi was supposed to blow himself up outside the canteen of the military base, while in a truck packed with a tonne of explosives. But his arrest at his Brussels flat on 13 September 2001, foiled the attack.
In his defence, Trabulsi’s lawyers asked for leniency since their client had not started to put his plans into place, and had since renounced violence.
However,prosecutors acknowledge that they have failed to prove that the alleged “Belgian cell” had planned the assassination of Afghanistan’s Northern Alliance chief Ahmad Shah Masood on 9 September 2001.