Paris, Oct 3 (IANS) A knife-wielding man on Thursday stabbed to death at least four police officers outside central police headquarters in Paris, before being shot dead, the media reported. The incident happened around 1 p.m. (local time) in the courtyard of the police building, which is located close to the Notre-Dame cathedral. The attacker, who was reported to be a member of staff inside the building, was shot dead by a policeman shortly after the assault, the BBC reported. The police headquarters was evacuated and a perimeter of security was put in place. The area in the île de la Cité -- in the centre of Paris was sealed. It comes a day after the French police went on strike across the country over increasing violence towards officers and rising suicide rates within the force.