The 56-year-old director of “La Haine” was following motorcycle training at the time, a police source told AFP.
He was taken to Kremlin-Bicêtre hospital, authorities in Essonne, south of the French capital, said.
French media reported that he had undergone motorcycle training to prepare for a role.
His injuries would be serious but not critical.
Kassovitz is best known for the hit 1995 film La Haine, which he wrote and directed at just 27 years old. Starring Vincent Cassel, Hubert Koundé and Saïd Taghmaoui, the film follows three men for 24 hours after a riot in the Parisian suburbs and won Kassovitz the prize. Best Director Award at the Cannes Film Festival.
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He also starred in the French spy series The Office of Legends (Le Bureau) which was a worldwide success, as well as in Munich by Amélie and Stephen Spielberg.