Justin Trudeau
Justin TrudeauReuters

Artists, activists and politicians on Wednesday appealed to Canadian Prime Minister Justin Trudeau to intervene to free the chief suspect in a deadly 1980 attack on a Paris synagogue.

Hassan Diab, 63, had been ordered discharged this week after the judge raised "doubts" about the evidence implicating him in the attack, but the decision was overturned on appeal.

In an open letter to Trudeau, nearly 300 Diab supporters urged the Canadian leader to prevent Diab's "wrongful conviction" and to help the "Canadian citizen unjustly imprisoned abroad return to his home in Canada."

The signatories include filmmakers Atom Egoyan and Sarah Polley, essayist and environmental activist Naomi Klein, author Yann Martel, former UN special envoy Stephen Lewis and former Canadian Liberal leader Bob Rae.

Diab, a Lebanese-Canadian sociology professor, is accused of being part of the special operations branch of the Popular Front for the Liberation of Palestine (PFLP) terrorist group, which carried out the bombing on October 3, 1980 that left four dead and around 40 injured.

Diab has been detained in France since being extradited from Canada in 2014. He claims he is innocent and denies being a member of the PFLP.

This week marked the eighth time, according to his lawyers, that Diab has been denied his freedom, which a member of his support committee, Roger Clark, described as "grotesquely absurd."

The prosecution has pointed to a sketch of the bomber resembling Diab, the discovery of a passport in his name with entry and exit stamps from Spain, where the bomber is believed to have fled, and testimonies that Diab was a member of the PFLP in the early 1980s.

Diab insists that he was in Beirut at the time of the attack, taking university exams, which witnesses have corroborated.

AFP contributed to this report.