The attack came as France remains in a state of emergency.
A man with a hammer attacked a police officer who was patrolling Notre Dame in Paris on Tuesday afternoon.
Another officer shot the assailant, who was taken to the hospital, the Associated Press reported. The incident took place around 4:30 p.m. local time, and was quickly followed by a police operation in the area, a police union spokesman told AP.
Police warned tourists to stay away from the area as they continue their investigation. Several hundred people were ushered inside the doors of the cathedral and held there as police subdued the attacker and swept the area, BBC reported.
“I was about to come inside [the cathedral] and heard the noise, the gunshots, turned around and saw the assailant on the ground where they had shot him,” Kellyn Gorman, an American tourist who was an eyewitness, told the BBC. “It was very safe, very quickly contained.”
French officials are treating the incident as a terror attack, the prosecutor's office said.
The incident comes just months after a police officer was shot and killed by an assailant on the Champs Elysées in an incident that was claimed by the Islamic State group. Two others were wounded in the attack.
France has remained in a state of emergency following a series of coordinated attacks in Paris in November 2015 that left 130 people dead and several hundred wounded.