According to French media, a history teacher was beheaded on a street in the town of Eragny, northwest of the French capital, around 5 p.m. local time.
The country’s anti-terror prosecutor called the incident a stabbing, but Reuters and AP news agencies reported the victim was beheaded, police sources said.
The victim, who is said to have taught at a nearby college, is said to have shown pictures of the Prophet Muhammad in class during a discussion on free speech.
Witnesses heard the attacker shout Allahu Akbar, or God is greater, Reuters said.
He was armed with a knife and an airsoft gun and was arrested about 600 meters from where the attack took place, AP said, citing a police official.
A Twitter thread posted last Friday, suspected students had seen caricatures of the prophet.
The thread contained a video of a man saying his Muslim daughter was one of the students in the class – and she had been shocked by the teacher’s actions.
Reuters said it had not been able to independently verify the authenticity of the video.
Le Parisien newspaper said the victim was “horribly mutilated”.
He also said the assailant was a parent of a student, but this was not confirmed by police.
Interior Minister Gérard Darmanin said he had set up a crisis center and was keeping President Macron informed.