“A 29-year-old man, of Afghan nationality, entered a restaurant on the beach of Le Havre in the late afternoon,” a police source told AFP.

“He was drunk and was not wearing a mask. A waiter asked him to put one on.

“He went outside, before returning and stabbing the waiter in the chest with a knife.”

The waiter, aged 30, was seriously wounded but his life was not in danger, the source added.

An off-duty police officer who intervened was slightly hurt. Police officers arrested the man as he left the bar and he is now in custody.

France, which is battling a resurgence of the coronavirus, has made wearing masks compulsory inside cafes, restaurants and most other indoor public spaces, as well as some outdoors.