Notre-Dame Cathedral was locked down after police shot and wounded a man who attacked an officer outside the tourist attraction.
Officers shot at the man after he had threatened them with a hammer and refused to stop, according to sources.
Police said the incident was over at around 5.30pm local time, and the attacker was taken to hospital.
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The officer was injured and the assailant was shot in the thorax, according to a source.
The French counter-terrorism office has opened an investigation after the incident at Notre-Dame Cathedral, the prosecutor’s office said.
Images from inside the Cathedral showed tourists with their hands in the air.
France is still in a state of emergency following the terror attacks in Paris which left 130 people dead in 2015.