A counter-terrorism investigation has been launched after French police shot and wounded a man who attacked officers with a hammer outside the Notre Dame cathedral in Paris.

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 French interior minister said the attacker shouted "this is for Syria" before being shot and injured.

Gerard Collomb also told reporters the attacker was found to be carrying kitchen knives and had a document identifying him as an Algerian student, the authenticity of which authorities were checking.

The incident 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 neutralised and taken to hospital," Paris police said on Twitter.

Two police sources said the officers shot the assailant in the chest 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.

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.