BRUSSELS: The trial of 10 men accused of participating in the 2016 Brussels bombings that killed 32 people began on Monday with defence lawyers arguing that their clients should not be put in glass boxes like animals in a zoo.

Monday's launch, in the former headquarters of NATO in a Brussels suburb, focused on procedural matters. The trial proper into the Islamist bombings at Brussels airport and on the city's metro in March 2016, with the indictments and testimony, is due to begin in October.

The special court for one of Belgium's largest trials features a series of individual glass compartments into which nine of the accused were placed on Monday.

The jury trial includes six men already convicted in June by a French court for their involvement in the 2015 Paris attacks that killed 130 people. 

They include Mohamed Abrini, who prosecutors say went to Brussels Airport in March 2016 with two suicide bombers, but fled without detonating his suitcase of explosives, and Osama Krayem, a Swedish national accused of planning to be a second bomber on Brussels' metro.

Sebastien Courtoy, lawyer for one of the accused, Smail Farisi, noted that his client had been acquitted of involvement in the Paris attacks but was being exhibited "like an animal in a cage" that observers would look upon as guilty.

"We are not defending Hannibal Lecter or a tiger that is ready to pounce on anyone," said Delphine Paci, defending Salah Abdeslam.

Abdeslam, the main suspect in the French trial, is also among the accused, along with others prosecutors say hosted certain attackers. The 10th man accused is presumed killed in Syria.

President judge Laurence Massart said she would rule on the glass compartments and other procedural points on Friday.

Massart asked the defendants to confirm their ages and previous addresses before most then returned to their cells. None of those present have been required to enter any plea, in line with Belgian court procedure.

Lawyers for victims of the attacks, including some 340 people injured, complained about the use of words such as "inhumane" to describe the treatment of the accused.

"For some victims it is particularly difficult to see how much attention is currently given to the accused. It is the whole time about the 'how' of the trial. The victims want it to be about the 'why,'" said Maryse Alie, lawyer for a group of some 500 victims.