One person has been killed and at least two police officers seriously injured in a knife attack in the eastern French city of Mulhouse.

A 37-year-old Algerian man was arrested at the scene and the prosecutor has opened a terrorist inquiry because the suspect reportedly shouted “Allahu Akbar”, or “God is great”.

The man injured two police officers seriously, one in the neck and one in the chest. A civilian who tried to intervene was stabbed and killed.

The suspect was subject to a deportation order because he was on a terrorism watch list, according to the local prosecutor. President Emmanuel Macron said there was “no doubt it was an Islamist terrorist attack”.

After expressing his condolences to the family of the victim, Macron said: “I want to reiterate the determination of the government, and mine, to continue the work to eradicate terrorism on our soil.”

The incident took place at a demonstration in support of the Democratic Republic of Congo, where the police officers were on patrol.

“Horror has seized our city,” Mulhouse mayor Michele Lutz said on Facebook.

French Prime Minister François Bayrou posted on X that “fanaticism has struck again and we are in mourning”.

“My thoughts naturally go to the victims and their families, with the firm hope that the injured will recover,” he said.

Interior Minister Bruno Retailleau is expected to visit the scene on Saturday evening.

Additional reporting by Tom Bennett and Rorey Bosotti