PARIS, JAN. 11 -- The French government put 20 alleged extremists on trial today in what was hailed as a demonstration of final victory over Direct Action, the country's main left-fringe terrorist organization.

The group trial, on charges of criminal association, was expected to provide a public autopsy of the now dismantled terror squad, which claimed responsibility for about 80 bombings and shootings since it was formed in 1979 to destabilize capitalist society and create a new order in France.

Although it remained small and never attracted a large following among members of legal leftist movements, Direct Action struck the public's imagination through high-visibility terrorist attacks until its leaders were captured last year. According to police and Direct Action communiques, these ranged from the assassination Nov. 17, 1986, of Georges Besse, head of the state-owned auto company Renault, to the murders of two policemen May 31, 1983.

Government critics, noting the criminal association charges and the peripheral role of some defendants, suggested that the large group proceeding against Direct Action was designed in part to provide a forum for underlining the success of Prime Minister Jacques Chirac's government in the battle against terrorism. The issue has become more than usually political here because some of those on trial had been released from jail under a widely condemned amnesty decreed in 1981 by the Socialist government that preceded Chirac's.

"Why this trial?" asked Daniel Schneidermann in Le Monde newspaper. "First of all, for image. All French terrorism pilloried for 15 days several months from the presidential election -- what a beautiful sucess for the government and its leader."

Direct Action's chief leaders and actors -- Jean Marc Rouillan, Nathalie Menigon, Georges Cipriani and Joelle Aubron -- were arrested last Feb. 22 in a remote farmhouse in a raid that police said decapitated the organization and put it out of operation. The four are awaiting separate trials on more serious charges, ranging from possession of explosives to murder, but also were included among the defendants put on trial today for illegal association.

Police carried Aubron into the guarded courtroom, where she sat with other defendants behind plexiglass shields. Aubron, Rouillan, Menigon and Cipriani have been on a hunger strike for several weeks to press demands for status as political prisoners.

Menigon shouted repeatedly as she was led into the courtroom and another defendant, identified as Jean Asselmayer, raised his fist in what appeared to be a gesture of defiance. Reporters said they heard one defendant scream "Class justice!" and another, "This is better than Chile!"

Illegal association, which carries a maximum sentence of 10 years in prison, has been defined in French law as participation in an association or understanding formed with a view toward preparing a concrete offense that was actually carried out. The defendants whose trial began today included lesser-known sympathizers accused of providing lodging or other logistics support to Direct Action members as well as those accused of actual terrorist crimes.

Maxime Frerot, another top Direct Action member regarded as the group's main explosives expert, was arrested Nov. 27 in an underground parking lot in Lyons. Because preparations for today's trial were already under way when he was captured, Frerot was not included in the list of 20 and will be tried on more serious charges separately, judicial sources said.

The final Direct Action leader police say is still at large, Mohand Hamami, is being tried in absentia. Acquitted several years ago of more serious charges linked to the policemen's murders, he reportedly has taken up residence in Algeria, out of the reach of French police.

Another member of what police called Direct Action's activist hard core, Regis Schleicher, was convicted by a special antiterrorism tribunal and sentenced to life imprisonment last June for his role in the policemen's murders. He also was included in today's trial.