A man has been stabbed in a suburb north-west of the French capital Paris, media reports say, with the attacker shot dead by police.
Reports suggest the victim in Conflans-Sainte-Honorine was beheaded but police have not confirmed this.
He is said to be a teacher who showed caricatures of the Prophet Muhammad in a classroom, media reports say.
The French anti-terrorist prosecutor has been called in to lead an investigation.
France’s Interior Minister Gerald Darmanin, travelling to Morocco, is returning urgently to Paris.
The attack occurred at about 17:00 local time (15:00 GMT) near a school.
Police arrived at the scene after receiving a call about a suspicious individual loitering near the school, a police source was quoted as saying by AFP news agency.
The French news agency says the officers found the victim and then sighted the suspect about 200m (220 yards) further in Eragny. He was threatening them with a knife-like weapon. The attacker was then shot dead by police.
The scene is now sealed off, as the investigation continues.