Paris police on Tuesday warned people to stay away from the city's Notre Dame cathedral after an officer reportedly opened fire on a man who tried to attack him with a hammer in the square in front of the building, security sources told EFE.

According to police, the officer who had been targeted was injured and the assailant was wounded by the gunfire, though no details were given on his condition.

"Situation under control in the area of Notre Dame, one police officer injured, assailant has been neutralized and taken to the hospital," police said on their official Twitter account.

According to media reports, the man tried to attack an officer with a hammer before being shot down.

The French counter-terror prosecutor's office said investigation into the incident had been opened, judicial sources told EFE.

According to an EFE correspondent on the ground, police forces have created a security perimeter around the Gothic masterpiece Notre Dame and its surroundings, located at the heart of the French capital.

Dozens of vehicles belonging to the French rapid response team could be seen from the police cordon.

Speaking to EFE, a Spanish tourist who was at the cathedral at the time of the attack described how security forces shut the doors to the building and did not allow anyone to enter or leave, explaining to visitors that there had been an incident outside.

"We heard the gunshots, but we thought it was thunder," she said, adding that they were still inside the cathedral, awaiting permission to leave.

She said people seemed to be calm and were sitting around as they waited for more information.