His long black hair and beard were in stark contrast to the cropped, clean-shaven man familiar from police images.
"I do not wish to answer any questions", the Brussels native told the judge, according to AFP.
On Monday, Ayari told the court he had fought for the Islamic State in Syria.
Anti-terrorist judges and police were hoping the trial today would shed light on the way groups like Isis operate in Europe, but Abdeslam is adamant that he will not cooperate. "Judge, do whatever you want with me, I put my trust in Allah", he added as a culmination to a plea against alleged demonization of Muslims. "I defend myself by staying silent".
Reciting the Islamic profession of faith and flanked by two masked Belgian counter-terrorism police officers, he said Muslims were treated "without mercy" and presumed guilty.
Abdeslam urged the judges to consider "scientific and tangible proof" while deciding on his case, saying that otherwise they would "give up their function to the media". "There is no presumption of innocence", he said.
The refusal to engage with the court may leave many disappointed.
French prosecutors believe Abdeslam played a key role in the Paris attacks, in which gunmen and bombers targeted a concert hall, stadium, restaurants and bars, the BBC reports. In all, that sprawling network of IS fighters killed 162 people in the two European capitals.
His brother was one of the group thought to be behind the attacks.
Abdeslam faces charges of attempted terrorist murder from the gun battle with police and carrying banned weapons.
He was detained in a raid in the western Brussels district of Molenbeek.
The trial is being held at the Palais de Justice in central Brussels under high security.
"These are undeniably tough security measures, but they are simply the effect of the police's assessment of the security need for the trial". Three officers were wounded in the shootout that followed and one suspect was killed. A suspect armed with an assault rifle was killed.
Police say the letter shows Abdeslam was planning further attacks.
In Brussels, he is facing separate attempted murder charges stemming from a 2016 police shootout four months after the Paris attacks.
Tight secrecy surrounded the plans for transferring Abdeslam from Fleury-Merogis prison in the Parisian suburbs, and then back to a prison just across the border in northern France every night.
In the letter, Abdeslam wrote: "Of course I wanted to be among the shahid [martyrs]".
It was a homecoming of sorts, Abdeslam's return to the city of his birth where he was dramatically shot in the leg and captured after four months on the run following the Paris attacks.
What about the Brussels attacks?
During that time, he eluded arrest, going from house to house across Brussels, before almost being cornered on March 15, 2016, when several police officers were shot and wounded.
Federal prosecutors in Belgium are seeking 20-year prison sentences for both men, formally citing a terrorist link in the shootout.
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