Hassan Diab
Hassan DiabReuters

A French court on Tuesday ordered the chief suspect in a deadly attack on a Paris synagogue in 1980 to be sent back to jail, ten days after he was released on bail, AFP reports.

Hassan Diab, a Lebanese-Canadian sociology professor who had been detained for 18 months, 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.

Targeting the synagogue in rue Copernic, western Paris, it was the first major attack on a Jewish site in France since World War II.

Diab, 62, was extradited from Canada in November 2014 and charged with the attack. He maintains his innocence and denies he was a member of the PFLP.

On May 12, a judge authorized his release on bail after ruling there was doubt over the "fundamental question" of whether he was in France on the day of the attack.

His ex-wife had told investigators that he was in Beirut on September 28, 1980, despite stamps in his passport indicating that he was already in Europe.

Federal prosecutors appealed the May 12 decision, leading an appeals court Tuesday to order him sent back to jail.

"It's a very unfair decision," Diab's lawyer William Bourdon said, according to AFP.

Bernard Cahen, lawyer for one of the civil parties to the case, said that "on the merits of the case, we are absolutely convinced of his guilt".

"The defense will struggle to destroy this case," he added.

Diab has been charged with murder, attempted murder and destruction of property as part of a terrorist enterprise.

AFP contributed to this report.