PARIS (Reuters) - The counter-terrorism unit of the Paris prosecutor's office opened an investigation on Tuesday, shortly after a man armed with a hammer attacked an officer outside the Notre Dame cathedral.
Police shot the assailant who was described as "neutralised" by the interior ministry.
A witness in a flat overlooking the site told BFM TV the attacker could be seen lying motionless on the ground. Armed police sealed off the area.
Reporting by Emmanuel Jarry; Editing by Richard Lough