A teacher has been beheaded in a suburb north-west of the French capital Paris, reports say, with the attacker shot dead by police.
The victim in Conflans-Sainte-Honorine was a teacher who is said to have shown caricatures of the Prophet Muhammad to his students.
The anti-terrorism prosecutor has been called in to lead an investigation into the attack.
The incident occurred at about 17:00 local time (15:00 GMT) near a school.
French President Emmanuel Macron is to visit Conflans-Sainte-Honorine later on Friday evening.
Interior Minister Gerald Darmanin, travelling to Morocco, is returning urgently to Paris.
France's AFP news agency, quoting police and prosecutors, said the victim had been decapitated.
A man wielding a large knife is reported to have attacked the teacher in a street, cutting off his head. The attacker then ran off, but local police alerted by the public were quickly at the scene in the nearby area of Éragny
When they shouted at him to give himself up, he is said to have threatened them. The officers shot him and he died a short time after,
The scene is now sealed off, as the investigation continues.
In a tweet (in French), police urged members of the public to avoid the area.
A trial is under way in Paris of alleged accomplices in the deadly 2015 attack on the satirical magazine Charlie Hebdo, which had published cartoons of the Prophet Muhammad.