Belgium on Monday began the trial of seven alleged jihadists accused of links to the terror cell behind the Paris and Brussels attacks.
The men were arrested after a deadly raid in the Belgian town of Verviers in January 2015 which exposed an alleged plan to kill police officers.
A further nine people who are still at large are being tried in their absence by the court in Brussels.
Police believe Abdelhamid Abaaoud, the suspected ringleader of November`s Paris attacks, was giving orders to the Verviers cell by phone from Greece.
Abaaoud, who was killed in a shootout in Paris days after the attacks, also had close links to the cell behind the March 22 Brussels airport and metro attacks.
French President Francois Hollande has said the same terror cell was behind the Paris massacre, in which gunmen and suicide bombers killed 130 people, and the Brussels attacks in which 32 people died.
Both attacks have been claimed by the Islamic State jihadist group.
“The theory in which Verviers is at the heart of the Paris attacks” is among those being probed by French legal authorities, a source close to the investigation told the French newspaper Le Monde.
The main suspect at the trial of the Verviers cell is Marouane El Bali, who is accused of attempted murder for firing at police during the gunfight, during which two suspected jihadists were killed.
He denies the charges.
“He was a small player and was absolutely not aware of any planned attacks,” his lawyer Sebastien Courtoy told Belga news agency.
Belgian police said at the time the cell was planning to kill and kidnap police officers under orders from Islamic State.