A knife-wielding man has killed four staff at police headquarters in the centre of the French capital, Paris.
The attacker, who has not been named but is said to also be an employee there, was later shot dead by police.
Witnesses described scenes of panic, with many people fleeing the building in tears. The area in the île de la Cité has been sealed off.
The attack comes a day after police went on strike across France over increasing violence towards officers.
There has been no official statement so far on a possible motive for the attack.
However, police union officials have suggested the attacker may have been involved in a workplace dispute.
What happened?
Paris Mayor Anne Hidalgo confirmed on Twitter that "several people" had been killed in the attack, which took place near major tourist sites including the Notre-Dame cathedral.
Three men and one woman were the victims, according to French broadcaster BFMTV.
Another person was also wounded.
At about 13:00 local time (11:00 GMT; 12:00 BST), the attacker is said to have gone into the building and straight to his office where he began attacking colleagues with a knife.
BFMTV reports that he stabbed two people inside two offices, one person on a stairway and the fourth person inside the building's courtyard - where the knifeman was shot dead by officers.
"Police were running around in panic," a witness who was inside the courtyard at the time of the attack told Le Parisien newspaper.
"I was surprised to hear shooting because this is not a place where you hear that kind of thing. I first thought it was a suicide because there are a lot of those at the moment," he added.
President Emmanuel Macron, Prime Minister Edouard Philippe and Interior Minister Christophe Castaner have all gone to the site.
Who was the attacker?
According to French media, he was a 45-year-old man who had worked in an administrative capacity for the Paris police force for 20 years.
They said he had been working in the force's intelligence division.
There were tensions between the knifeman and his supervisor, according to police union official Christophe Crepin.
"I do not think this is a terrorist act," Mr Crepin, who knew the attacker, told Franceinfo Radio.
Police union leader Jean-Marc Bailleul described it as a criminal act, telling BFMTV: "It was a moment of madness."
The attack follows a rare nationwide police strike on Wednesday, which saw thousands of officers demonstrating in Paris over working hours, shortages in resources and controversial pension reforms.
Media captionFrench police get angry over working conditions and suicide rates
Police unions say there have been more than 50 suicides by police officers since the start of the year.
They blame the rising numbers on difficult working conditions and increasing violence towards police.
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