French Foreign Minister Jean-Yves Le Drian said Saturday that missile strikes carried out overnight in Syria by Britain, France and the US had destroyed a "large part" of the Damascus government's stocks of chemical weapons.

"A large part of its chemical arsenal has been destroyed," Le Drian told BFM television. "A lot has been destroyed in last night's strikes."

He also said France had "solid intelligence" that the regime of Syrian President Bashar al-Assad was behind the gas attack in the rebel-held city of Douma last weekend, which monitors say killed at least 40 people.

"On the question of chemical weapons, there is a red line that must not be crossed, and if it should be crossed again, there will be another intervention," Le Drian said.

"But I think the lesson has been learned."