The chat group allegedly discussed targets, which included the headquarters of the Jewish council (CRIF) and the office of the anti-Jewish discrimination league (LICRA).
The group’s online discussions are alleged to have also included hatred of Muslims and communists as well as comments that were antisemitic and homophobic.
The four men include a farm worker, as well as an engineering student who was the son of an army colonel.
The court heard how the group's alleged leader was Alexandre Gilet, a volunteer deputy police officer in the southeastern department of Isere.
Gilet was arrested after police learned he had ordered equipment that could be used for making explosives, according to AFP.
At his home, investigators found "regularly used" weapons. These included two Kalashnikov assault rifles and lab equipment.
Investigators found 'regularly used' weapons at Gilet's home including two Kalashnikov assault rifles and lab equipment (Photo: Getty)
French media also reported that investigators found pictures of the four men when they had met face-to-face for the first time in the summer of 2018 for shooting practice in a forest near Tours.
In addition, they found draft documents that they interpreted to be manifestos along the lines of those used to justify ultra-right mass killings.
A closed-door trial for all four men was likely but presiding judge Christophe Petiteau said that given the seriousness of the allegations, “the court considers it important to lift the restricted publicity”.
One of the suspects would later say of Gilet: “I think he wanted to do something worse than the Bataclan.”
He was referring to the November 2015 jihadist attacks in Paris in which 130 people were killed, dozens of them at the Bataclan concert venue.
Lawyers for the four men are due to argue in court they would not have carried out any real attacks, nor had they written manifestos.
The trial continues until June 30.
