A man was shot by police outside Paris's Notre Dame Cathedral on Tuesday afternoon after he attacked officers with a hammer.
The man, who has not been identified, is believed to have attacked an officer who was patrolling with two other policemen at about 4.30pm local time.
One of the officers responded with two gunshots, which injured the assailant.
The motive for the attack was not immediately known.
Police union official Cedric Michel said the man armed with a hammer went after the police officer who was patrolling on the esplanade in front of Notre Dame Cathedral.
Police sources said the officers shot at the man after he refused to stop threatening them with the hammer.
It is unclear whether the attacker was acting alone.
One officer was lightly injured and the assailant was shot in the chest, according to one source.
Footage seen on social media showed the assailant lying on the ground after being shot.
Emergency responders were on scene after the incident, according to Europe 1.
Police had earlier said they were dealing with an incident in the courtyard outside the world-famous tourist site amid reports of panic and gunshots in the area.
Officials warned people to stay away from the area after saying there was an 'incident' at the popular tourist destination.
At least one person on the scene said on Twitter that he was inside the church and could hear sirens outside.
'So we are trapped in Notre Dame Cathedral,' Matthew CurrieHolmes, a tourist from Los Angeles, wrote on Twitter. 'Something is happening outside we don't know what it is. Police sirens can be heard.'
CurrieHolmes, who was also in London during the terror attack on Saturday, later said everyone was safe but that officials were not letting anyone in or out of the cathedral.
People inside the church were told so sit down and put their hands up as police investigated the attack.
Photos on social media show rows of dozens of people sitting in wooden chairs with their arms up.
By 5.30pm local time, an hour after the attack, CurrieHolmes said that he and other visitors were being let out of the cathedral.
'They started to let everyone out! Everyone is save,' CurrieHolmes wrote on Twitter. 'Please do not disseminate false information.'
The police department tweeted about the operation on Tuesday afternoon but did not provide any details. A police official would not provide further information.
Large numbers of police cars filled the area on the Ile de Cite island in the River Seine in the center of Paris.
Witnesses around Notre Dame Cathedral have described the dramatic police operation in the tourist-filled site in central Paris.
Lawrence Langner, a 73-year-old American visiting the neighborhood just across the Seine River from the cathedral, told The Associated Press that he suddenly heard a commotion and two detonations like gunshots.
Journalist David Metreau, who said his office overlooks the square, tweeted that there were two blasts that sounded like shots, and posted a photo of a body lying seemingly inert on the ground.
Others posted photos online of what appeared to be the interior of medieval Notre Dame, one of France's most-visited monuments.
France remains on high alert after a series of deadly terror attacks in recent years.