Local prosecutors said one person was killed and two police officers were seriously injured in a knife attack during a demonstration in eastern France.
French President Emmanuel Macron said it was “undetectedly an act of Islamist terrorism.”
Three more officers were minor injuries on Saturday afternoon, a man attacked a local police officer in Malhaus city, yelling “Arafu Akbar” and meant “God is the greatest” in Arabic .
Passersby said he was killed trying to intervene.
The suspected attacker who was arrested is on the terrorist prevention watchlist, prosecutor Nicholas Heights told AFP.
This list compiles data from various authorities on people to prevent the radicalization of terrorists. It was released in 2015 after a fatal attack in the satire magazine Charlie Hebd's office and Jewish supermarket.
One of the seriously injured officers suffered a carotid injury and the other injured in the chest, Heights said.
Home Minister Bruno Reciro was expected to travel to the scene of the attack later Saturday.
Police established security perimeters after the attack. This happened before 4pm during a pro-Congo demonstration.
The suspect was Algerian and was under judicial oversight and arrested House of Representatives and ordered to expel him from France, according to union sources.
“Horror seized our city,” Mulhouse Mayor Michèle Lutz told Facebook. The incident was being investigated as a terrorist attack, she said, but “this clearly still needs to be confirmed by the judiciary.”
France's National PNAT said it was in charge of the investigation.
