Knife attacker kills 4 police at Paris HQ

Four officers have died in a knife attack by an administrator at the Paris police headquarters, a police union official says, the attacker has been shot dead.

It wasn't immediately clear how far the assailant got inside the building, which is located across the street from Notre Dame Cathedral.

Union official Loic Travers said the attack on Thursday appears to have begun in an office and continued elsewhere inside the large compound across the street from Notre Dame Cathedral.

Travers says the motive is unknown, but the employee allegedly responsible for the violence apparently never posed any problems before.

He says he can't remember an attack on police officers of this magnitude.

Jean-Marc Bailleul, another union leader, described the incident as criminal rather than an act of terror. "It was a moment of madness" Bailleul told BFM TV.

The attack came a day after thousands of officers marched in Paris to protest low wages, long hours and increasing suicides in their ranks.

The area around the police headquarters was sealed off and the nearest metro station was shut for security reasons, the transport authority said.

President Emmanuel Macron is expected to visit the scene later, as are the country's interior minister and the Paris prosecutor.

Extremists have repeatedly targeted French police in France in recent years. In 2017, a gunman opened fire on the Champs-Elysees boulevard, killing one officer before he was shot to death.

In 2016, an attack inspired by the Islamic State group killed a police officer and his companion, an administrator, at their home in front of their child.