Paris police say an officer shot and wounded an unidentified assailant who attacked him with a hammer near Notre Dame Cathedral on Tuesday.

A police spokesperson told The Associated Press that the officer used his weapon to shoot the attacker in Tuesday’s incident. The spokesperson, who was not authorized to be publicly named, said the attacker was being hospitalized.

A police union official, Cedric Michel, said a man armed with a hammer went after the police officer who was patrolling on the esplanade in front of Notre Dame Cathedral. Michel said the attacker was “neutralized” by police.

It is unclear whether the attacker was acting alone.

Earlier, Paris police said a security operation was under way near Notre Dame Cathedral and urged passers-by to stay away from the area. The police department tweeted about the operation on Tuesday afternoon but did not provide any details.

Large numbers of police cars filled the area on the Ile de Cite island in the River Seine in the center of Paris.The city has been under high security after a string of Islamic extremist attacks in recent years.