A car has crashed into a police van before bursting into flames around the Champs Élysées area of central Paris, police officials say.
The driver, who had a weapon inside the car, was knocked unconscious and is seriously injured, French media report.
Police say the situation is now under control, and neither law enforcement officers nor civilians were injured.
France is under a state of emergency after being hit by a wave of deadly terror attacks in recent years.
A policeman was shot dead and two others were wounded in an attack on the Champs Élysées in April, just days before the presidential election.
French media, quoting police sources, say the incident on Monday was deliberate.
A white car is standing in the middle of the empty avenue with one door open and sniffer dogs have been sent in, the BBC’s Hugh Schofield reports from Paris.
Reports say officers had to smash the windows of the car to pull the driver out.
Our correspondent says there are always many police and gendarme vehicles near the spot, as it is next to the local police station.
The national police Twitter account had earlier said (in French) that there was an “ongoing police operation”, warning people to respect the security cordon.
The anti-terrorist section of the prosecutor’s office has opened up an investigation.
Interior Minister Gérard Collomb tweeted a picture of himself at the scene of the “attack aimed at our security forces”.