Legendary French actor Alain Delon is "getting better and better", one of his sons has assured fans, after the 83-year-old suffered a stroke.

Posting a photo of the actor, known for his starring roles in films such as "The Swimming Pool" and "Purple Noon", on his Instagram account late Sunday, Alain-Fabien Delon thanked his father's fans for their support.

"Thank you for your many messages, which have deeply touched me. As you can see, he is getting better and better. And he sends you his love," the post said, with a picture of the actor sitting up, wearing a red polo shirt and smiling.

On Thursday, Delon's eldest son Anthony had said the actor had suffered a stroke a few weeks ago and was currently "resting" in Switzerland.

Then a day later, his daughter Anouchka had said Delon was "already thinking about his next projects".

He has spent over 60 years working in European cinema.