Members of the "Cannes-Torcy cell" were brought to the special anti-terror tribunal on Thursday to face terror charges against them.
Cannes and Torcy are the names of the two towns where its members were based.
The 20 men on trial are suspected to be behind a grenade attack on a Jewish grocery store in 2012 with plans to carry out several more attacks on military and civilian targets, and of seeking to join Takfiri terrorists fighting the Syrian government on behalf on U.S, Saudi Araia, Israel and E.U.
Ten of the suspects are being kept in prison, seven have been released on bail pending trial, while three others are at large, two of whom are believed to be in Syria.
The terrorists are battling the Syrian and Iraqi governments. They have also carried out several terrorist attacks in some European cities.
Most of the suspects linked to the "Cannes-Torcy cell", who are all aged between 23 to 33 years, will be facing terms ranging from 30 years to life in prison if convicted.
Two of the suspects were arrested in connection with the grenade attack on the Jewish grocery in the Paris suburb of Sarcelles in September 2012.
Police also found bomb-making equipment in a storage unit rented by Jeremie Bailly, the alleged leader of the group.
Another suspected member, Jeremie Louis-Sydney, was killed in October 2012 when police came to arrest him at his apartment in the eastern city of Strasbourg.
The trial is expected to run until July 7.
France has been in a state of emergency since a series of deadly attacks hit Paris in November 2015.
Authorities plan to further beef up security measures to ensure that no terrorist activities occur on the day of its presidential election later this month.
France is among the Western countries that have been supporting the terrorists fighting to topple the Syrian government.
Eager to see the back of the Syrian government, many European countries turned a blind eye to the flow of their citizens to the Middle East, ignoring warnings that they would return home someday.