Police have shot and wounded a man who attacked an officer with a hammer while shouting “this is for Syria” outside historic Notre Dame cathedral in Paris on Wednesday morning AEST.

Tourists inside the cathedral were locked down after the attacker was shot twice in what officials fear is another incident in the wave of terror gripping Europe.

“A man came behind these police officers and, armed with a hammer, started hitting one of them. His colleagues reacted with composure … and fired,” French interior minister Gerard Collomb told reporters near the cathedral.

Collomb added that the injured attacked was being treated in hospital and seemed to have acted alone.

A woman interviewed from inside Notre Dame by Britain’s Sky News told of hearing shots and screams, then seeing a human wave of fearful sightseers pour into the cathedral for shelter.

Others fled from the open plaza, with one witness describing the spontaneous evacuation as “verging on a stampede”.

French officials have not confirmed initial reports, but were quoted unoffically as saying the attacker might have hoped to strike down the gendarme and seize his weapon.

The BBC reported the attacker inflicted two hammer blows to the officer’s head before being shot, when he was found to be carrying “a number of knives.”

As of early this morning, French TV was reporting order had been restored in the area and there was no known imminent threat.

Tourists who took refuge in the cathedral were being checked by police before being allowed to leave.

Always tight, security in and around the tourist mecca had been stepped up in the wake of recent Islamist attacks on Manchester and London.

Notre Dame, famous for its picturesque gargoyles, is located on an island in the Seine and attracts an estimated 14 million visitors very year, making it Europe’s most visited attraction.