1 of 2
Virginia Mayo, Associated Press
Co- defendant and key witness Jejoen Bontinck, center left, arrives with his lawyer Kris Luyckx to the main courthouse in Antwerp, Belgium on Monday, Sept. 29, 2014. Dozens of Belgians on Monday are going on trial accused of leading or being members of a terrorist organization that allegedly recruited fighters for jihadi groups in Syria. The case, one of the biggest-ever terror trials in Belgium, centers on the radical Muslim group Sharia4Belgium and its members.

ANTWERP, Belgium — A radical Muslim organization in Belgium was a well-structured terror group that brainwashed youngsters and sent them to fight in Syria, prosecutors said Monday as a trial started for dozens of suspects.

Only eight of the 46 suspects of the Sharia4Belgium group were present for the trial's opening. Many others are believed to be fighting in Syria or to have died in the country's civil war.

The group's alleged leader, Fouad Belkacem, who is in custody, was led into court by armed guards. He listened in silence to prosecutor Ann Fransen as she said that leading a terror organization has a maximum sentence of 15-20 years.

The case, one of the biggest-ever terror trials in Belgium, centers on Sharia4Belgium and its efforts to indoctrinate young Muslims and send them to Syria to fight.

Many members of the group left in August 2012 to fight in Syria, Fransen said.

"This mass departure is a logical and desired result of the indoctrination process," Fransen told a three-judge panel in a packed Antwerp courtroom.

Quoting from tapped phone conversations and statements by one of the suspects, who will be a key prosecution witness, Fransen said the Belgians were deeply entwined with al-Qaida-inspired Sunni Muslim groups fighting in Syria that have become the Islamic State group and are now being targeted by U.S.-led airstrikes.

Dozens of Belgians are believed to have traveled to Syria to fight and authorities fear they will return home battle-hardened and trained to carry out attacks.

Similar fears are held across Europe, and Fransen said Sharia4Belgium had links with like-minded groups in Britain, the Netherlands, France and Germany.

The group was disbanded nearly two years ago. Prosecutors now want to prove it was a terror organization.

Defense lawyers for the suspects who are in court will make their arguments Tuesday.