One of more than 50 men accused of raping Frenchwoman Gisele Pelicot in a mass rape case that has shocked the world told her in court on Thursday that he was sorry for what he did.

Lionel Rodriguez is among a small number of those accused who have admitted to raping Pelicot, who was abused by dozens of strangers over nearly a decade while knocked unconscious by drugs her husband Dominique gave her without her knowing.

Dominique Pelicot, who recruited the strangers online and invited them to the couple's family house to rape his wife, admitted to his crimes in court on Monday, saying: "I am a rapist, just like the others (the accused) in this room."

Rodriguez, aged 44, and a father of three, said on Thursday, speaking to the 72-year-old Gisele Pelicot: "I am sorry, I can only imagine the nightmare you've lived through... and I am part of this nightmare. I know my apologies won't change what happened, but I wanted to tell you that."

The case has triggered protests across France in support of Gisele Pelicot, who asked for the trial not to be held behind closed doors in order to shed light on the abuse.

The fact that dozens of seemingly ordinary men, currently aged 26 to 74, and from all walks of life, could rape an unconscious woman has attracted worldwide attention and turned the trial into a symbol of the pervasiveness of sexual violence.

Rodriguez admitted during the investigation that he had raped Gisele Pelicot. In court on Thursday, he repeated that he had not meant to rape her but realises that he did.

"If I had known she wasn't aware (of what would happen) I wouldn't have gone there," he said. "I should have checked that she was okay with it. I didn't talk to her, so I could not get her consent. I feel guilty for what I did."

"I never told myself: I will rape that woman," he said. But "I'm guilty of rape," he said, adding he should have left when he saw she was unconscious, and that it was cowardly of him not to have said anything.

Rodriguez also tried to shift some of the blame onto Dominique Pelicot, telling the court he had done what the husband had told him to do.