Paris Notre-Dame attacker shouted 'this is for Syria'

A hammer-wielding attacker who tried to assault a French police officer outside the capital’s Notre-Dame Cathedral before being shot, allegedly shouted 'this is for Syria', a French minister said on Tuesday.

The man who attacked the officer with the weapon outside the iconic tourist hot-spot was injured by the gunshot and was reportedly transported to a hospital, authorities said, giving the all-clear.

"The situation is under control," Paris police said on Twitter, adding that hundreds of people who were kept inside the famous cathedral would be progressively let out after routine checks.

Anti-terrorist prosecutors have opened an investigation into the attack, reports suggested.

France, which has been repeatedly targeted by Islamic State militants since 2015, has remained in a state of emergency, increasing its security presence nationwide.

In April, an attacker with an automatic weapon opened fire on police in Paris' iconic Champs-Elysees shopping district, killing one officer and seriously wounding two others before police shot and killed him.

Police and soldiers sealed off the area, ordering tourists back into their hotels and blocking people from approaching the scene.