PARIS:A French court has ruled that Clint Eastwood cannot testify during the trial of a suspected Islamist gunman, whose attack on a high-speed train was thwarted by three Americans, who later played themselves in a movie by the U.S. actor and director.

The trial of Moroccan national Ayoub el Khazzani, who opened fire aboard a Thalys train travelling through Northern Europe in August, 2015, started on Monday in Paris.

Khazzani's lawyer had asked before the trial began that the court call Eastwood as a witness, claiming that he could "shed some light" on the authenticity of scenes depicted in his movie.

Eastwood's movie is based on a book written by the trio entitled "The 15:17 to Paris: The True Story of a Terrorist, a Train, and Three American Heroes".

Khazzani told investigators before the trial he decided against the attack at the last second but that it was too late to avoid the confrontation with passengers, a judicial source has said.

The movie however does not show this claimed change of heart. The defence lawyer feared the film could influence people's view of the attack. She wanted to question Eastwood on what instructions he had given as a director to the actors.

Anti-terrorism prosecutors opposed the lawyer's request. They said Eastwood had not witnessed the incident and that it made no sense to call on a 90-year-old in the midst of a pandemic. They accused the defense of seeking to "to create a buzz".

The judge refused the request, arguing that Spencer Stone, Anthony Sadler and Alek Skarlatos, the young Americans who immobilised Khazzani before anyone was killed, would testify on Thursday and Friday.

The three men were awarded a medal of honor by then French president Francois Hollande, along with Mark Moogalian, a French-American professor who was shot in the back by Khazzani with a handgun after snatching his Kalashnikov rifle.

Moogalian, who is now 56, will also appear as a witness on Thursday.