Armed police cordoned off the site and the cathedral in central Paris that is visited by millions of tourists every year was locked down during the incident.
The motive for the attack was not immediately clear. It comes just three days after militants killed seven people in London in a knife and van attack.
London terror attack death toll rises to seven
"Situation under control, one policeman injured, the assailant was neutralised and taken to hospital," Paris police said on Twitter.
🔴 Parvis de #NotreDame Situation maîtrisée, un policier blessé, l'auteur des faits a été neutralisé et orienté vers un hôpital
— PrĂ©fecture de Police (@prefpolice) June 6, 2017
Two police sources said the officers shot the assailant in the thorax after he had threatened them with a hammer and refused to stop.
French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. PHOTO: REUTERSÂ
One policeman was hurt, according to one source. Karine Dalle, a spokesperson for the Paris diocese, told BFM TV 900 people were still inside the cathedral as police secured the area.
One holidaymaker inside Notre Dame wrote on Twitter: "Not the holiday experience wanted. Trapped in Notre Dame Cathedral after police shoot a man. We are with our 2 terrified children."
Police officer killed, another wounded in Paris shooting
France is under a state of emergency after a wave of militant attacks since early 2015 that have killed more than 230 people across the country. It has soldiers patrolling its streets alongside police to protect tourist sites, government buildings and events.
Three women were arrested in September after police found a car laden with gas cylinders abandoned near Notre Dame cathedral in what the interior ministry at the time said was a likely planned imminent attack.
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