PARIS, June 6 (Reuters) - French police shot and wounded a man who attacked officers with a hammer outside the Notre Dame cathedral on Tuesday, and the Paris prosecutor's office swiftly launched a counter-terrorism investigation.

The attacker was carrying an Algerian student card and shouted "this is for Syria" when he hit one officer, French interior minister Gerard Collomb said.

"A man came behind these police officers and, armed with a hammer, started hitting one of them. His colleagues reacted with composure...and fired," Collomb told reporters near the cathedral in central Paris.

9 PHOTOS Shots reported at Notre Dame Cathedral in France See Gallery Shots reported at Notre Dame Cathedral in France French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. REUTERS/Charles Platiau French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. REUTERS/Philippe Wojazer French police officials gather at the entrance to Notre-Dame cathedral in Paris on June 6, 2017. Anti-terrorist prosecutors have opened a probe after police shot and injured a man who had tried to attack an officer with a hammer outside Notre Dame cathedral. The officer was slightly injured in the attack outside the world-famous landmark in central Paris. One of his colleagues responded by shooting him, wounding the attacker, whose motives were not immediately known, according to a police source. / AFP PHOTO / Martin BUREAU (Photo credit should read MARTIN BUREAU/AFP/Getty Images) French police officials gather at the entrance to Notre-Dame cathedral in Paris on June 6, 2017. Anti-terrorist prosecutors have opened a probe after police shot and injured a man who had tried to attack an officer with a hammer outside Notre Dame cathedral. The officer was slightly injured in the attack outside the world-famous landmark in central Paris. One of his colleagues responded by shooting him, wounding the attacker, whose motives were not immediately known, according to a police source. / AFP PHOTO / bertrand GUAY (Photo credit should read BERTRAND GUAY/AFP/Getty Images) French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. REUTERS/Philippe Wojazer French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. REUTERS/Philippe Wojazer French police stand at the scene of a shooting incident near the Notre Dame Cathedral in Paris, France, June 6, 2017. REUTERS/Charles Platiau French police officials gather at the entrance to Notre-Dame cathedral in Paris on June 6, 2017. Anti-terrorist prosecutors have opened a probe after police shot and injured a man who had tried to attack an officer with a hammer outside Notre Dame cathedral. The officer was slightly injured in the attack outside the world-famous landmark in central Paris. One of his colleagues responded by shooting him, wounding the attacker, whose motives were not immediately known, according to a police source. / AFP PHOTO / Martin BUREAU (Photo credit should read MARTIN BUREAU/AFP/Getty Images) French police officials gather at the entrance to Notre-Dame Cathederal in Paris on June 6, 2017. A French police officer has shot and injured a man who attacked him with a hammer outside Paris's Notre-Dame cathedral authorities said. Police sealed off the area in front of the cathedral, where the attacker lay injured on the ground. / AFP PHOTO / Martin BUREAU (Photo credit should read MARTIN BUREAU/AFP/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

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 Islamist militants killed seven people in London in a knife and van attack.

"Situation under control, one policeman injured, the assailant was neutralized and taken to hospital," Paris police said on Twitter.

Two police sources said the officers shot the assailant in the thorax after he had threatened them with a hammer and refused to stop. One policeman was hurt, according to one source.

Karine Dalle, a spokeswoman 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."

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. (Reporting by Maya Nikolaeva and Emmanuel Jarry; writing by John Irish; Editing by Richard Lough)

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