Mehdi Nemmouche was found guilty of murdering four people at a Jewish museum in Belgium's capital. His alleged accomplice, Nacer Bendrer, was found guilty of supplying the revolver and assault rifle used in the killings.
A jury found Frenchman Mehdi Nemmouche guilty Thursday of the "terrorist murders" of four people at Brussels' Jewish museum, in the first case of a Syria militant to stage an attack in Europe.
Nemmouche, 33, now faces a life sentence for the anti-Semitic gun rampage in the Belgian capital on May 24, 2014, following his return from Syria's battlefields.
Sentencing is now not expected to take place before Monday, the court said.
Sporting a trimmed beard and wearing a navy blue sweater, Nemmouche showed no emotion and stared into space as the verdict was delivered.
The 12 jurors, accompanied by the presiding judge and two other magistrates, had deliberated for two and a half days in secret at a Brussels hotel before returning their verdict.
Nemmouche was found to have killed the four victims in cold blood in less than 90 seconds, but he denied the accusation telling the court he had been "tricked".
Presiding judge Laurence Massart, who read out the jury's verdict, said: "The existence of a trap was not presented with enough credibility and must be ruled out."
Nemmouche's lawyers had argued he was not to blame for the slaughter, but rather he had been caught up in some kind of plot targeting the Israeli intelligence agency Mossad.
The legal argument had centred around Israeli couple Miriam and Emmanuel Riva, the first two of the four people shot dead in the attack.
A young Belgian employee, Alexandre Strens, and French volunteer Dominique Sabrier were also murdered.
According to the defence, the museum shooting was not the work of Daesh but a "targeted execution" aimed at Mossad agents.
The defence said the Israeli couple who were killed were in fact Mossad agents murdered by another man who had hunted them down.
The Riva family's lawyers have furiously rejected the theory and said attempts to pass off the tourists as secret agents was "an absolute scandal".
Miriam Riva worked for Mossad but, as an accountant, she was not operational, said the investigating judges who travelled to Israel during their investigation.
'Set of scattered deductions'
Yohan Benizri, the head of Belgium's Coordinating Committee of Jewish Organisations, denounced what he called a "nauseating conspiracy theory".
The 12 jurors also found fellow Frenchman Nacer Bendrer, 30, who was accused of supplying the weapons, to be the co-author of the attack.
Seated next to Nemmouche in the defendant's box, encased by bullet-proof glass on the sides, Bendrer then hung his head low for a few minutes before covering it with his hands.
He also faces a life jail sentence.
The investigation showed that the two men had dozens of telephone conversations in April 2014, when Nemmouche was preparing for the killings.
Six days after the massacre, Nemmouche was arrested in the French city of Marseille in possession of a revolver and a Kalashnikov-type assault rifle.
At the trial, Bendrer admitted that Nemmouche had asked him for a Kalashnikov when he came to Brussels in early April, but claimed he never delivered it.
Among other personal effects, Nemmouche upon arrest carried a nylon jacket with gunshot residue, as well as a computer in which investigators found six videos claiming the attack with an off-camera voiceover thought to be Nemmouche.
The presiding judge singled out the evidence on his jacket which she said "contained exclusively traces of DNA from Mehdi Nemmouche".
In total, the prosecution said it had identified 23 pieces of evidence pointing to Nemmouche, who also physically resembles the shooter seen on the museum's surveillance video.
The verdict said: "The defence limited itself to outlining a set of scattered deductions without ever elaborating on them."
It added that Bendrer, by supplying the weapons, was aware of aiding a crime committed by "a longstanding radical," alluding to Nemmouche.
The prosecutors say the attack was the first carried out in Europe by a militant returning from fighting in Syria.
The Brussels killings came 18 months before the November 13, 2015, Paris attacks which left 130 dead.