Police are hunting a gunman who shot dead a policewoman and seriously hurt a street sweeper in the second "terrorist act" in France in as many days.
The attacker wore a bullet-proof vest and carried a handgun and automatic rifle in the shooting in Montrouge just south of Paris on Thursday morning.
But it was not being linked to Wednesday's attack on the Paris office of satirical magazine Charlie Hebdo that left 12 people dead, including two police officers.
The latest shooting happened after police and maintenance workers were called to the scene following a traffic accident involving a grey Clio just before 8am local time (7am UK time).
The gunman opened fire and the trainee policewoman, reportedly named Clarissa Jean-Philippe, 25, was shot dead. A street sweeper was seriously injured.
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Witness Ahmed Sassi, 38, who was watching from his kitchen window, said it was "a scene of panic".
He said he saw "a police officer standing in the road. A man with dark clothes shot them at point blank range, while continuing to run."
The shooting is now being treated as a "terrorist act" by the French authorities.
Security forces detained a man soon afterwards but he was not the shooter, police said.
They then raided a hotel room nearby but that operation was unsuccessful.
Interior minister Bernard Cazeneuve said authorities were doing their best to identify and arrest the attacker, and he urged people not to jump to conclusions about any link to the magazine shooting.
Meanwhile, officers are still hunting for two suspects in the earlier attack.
Two men matching their description are said to have robbed a petrol station about an hour's drive northeast of Paris.
Footage of police activity in the village of Crepy-en-Valois, 10 miles (16km) from that scene later emerged.
With the country now on its highest terror alert, hundreds of extra officers have been deployed to guard media offices, places of worship and other areas deemed at risk in the capital.
Some 200 soldiers from parachute regiments across the country have been drafted in to Paris, bringing the number of military patrolling the streets to 850.
A minute's silence was held across France in a mark of respect for the victims of Wednesday's violence.
Other attacks were also reported on Thursday - including a "criminal" explosion at a kebab shop near a mosque in eastern France.
Overnight into Thursday, two Muslim places of worship - in Le Mans, west of Paris, and Port-la-Nouvelle, in southern France - were targeted by blank grenades and gunfire respectively. No casualties were reported