At least four officers were killed in an attack on the headquarters of the Paris police

An employee at a Paris police headquarters has attacked officers with a knife, killing at least four before being shot, police union officials said.

Loic Travers, a union official, said one officer suffered fatal wounds and another officer shot the attacker in the historic building near Notre Dame Cathedral. The Ile de la Cité area was closed off by police and the nearby Cité metro station was closed and sealed off. Four officers were killed, the French news agency AFP reported.

The motives of the attack were not known. The interior minister, state prosecutor and prime minister travelled to the scene to be briefed and were expected to make a statement.

The president, Emmanuel Macron, went to the police headquarters to follow the investigation. He was expected to go ahead with his scheduled public debate on pensions reform in the southern town of Rodez on Thursday night.

French media reported that a staff member carried out the attack with a ceramic knife in a part of the prefecture that is not open to the public.

The man worked in an administrative capacity but it was not immediately clear what his precise work role was.

“People were running everywhere, there was crying everywhere,” said Emery Siamandi, and interpreter who was in the building when the attack happened.

“I heard a shot, I gathered it was inside,” he told AFP. “Moments later, I saw police officers crying. They were in a panic.”

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

Police were investigating and carrying out searches related to the attack. The interior minister has not yet commented or given a motive. French media quoted police union officials suggesting the motive may have been personal.

French police have been targeted by extremists in recent years. In 2017, a gunman opened fire on the Champs-Élysées in central Paris, killing one officer before he was shot dead.

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