A baby has died and 10 people have been injured after they jumped out of a second-floor flat window, apparently thinking they had seen the devil.
Police are investigating the incident which took place in the early hours in the small town of La Verriere, west of Paris.
The baby was four months old and officers said many of the injured were children.
"Thirteen people were in an apartment on the second floor when, at around 3am, one of the occupants heard his child crying," said Odile Faivre, the deputy prosecutor in Versailles.
"The man in question, of African origin, who was completely naked, got up to feed his child, at which point the other occupants took him for the devil.
The occupants tried to escape by jumping out of the window, panicked by a fear of the devil.
"He was seriously wounded in the hand after being stabbed with a knife before he was thrown out of the apartment, via the door."
The 30-year-old man then tried to force his way back into the room.
"That's when the other occupants tried to escape by jumping out of the window, panicked by a fear of the devil," said Ms Faivre.
Police are questioning the naked man as well as another man who jumped from the window with a two-year-old girl in his arms.
Seven of those injured - who were African, possibly from Angola - were taken to hospital for emergency treatment.
