The police shot and killed a man in northern France on Friday after he set fire to a synagogue in the city of Rouen and attacked officers who tried to stop him, the French authorities said.

Nicolas Mayer-Rossignol, the mayor of Rouen, a city of about 110,000 people, told reporters that firefighters had brought the outbreak of flames under control and that no one other than the assailant had been harmed.

The identity and motives of the man who attacked the synagogue were not immediately clear, but the French authorities were treating the incident as an antisemitic act. Local prosecutors have opened an investigation into “religiously motivated arson” and assault.

The authorities in France have raised the alarm about a surge of antisemitic incidents across the country in recent months, against the backdrop of the war in Gaza.

Gérald Darmanin, France’s interior minister, told reporters in Rouen that the fire was “obviously an antisemitic act.” He said the suspect was an Algerian man who had ignored an order to leave the country.

“No matter the threats the Jewish community faces, they must know that they are protected,” Mr. Darmanin said.