Dozens of cars and several buildings were torched in Nantes overnight as the western French city was rocked by a third night of rioting after police shot dead a young black man.
Tuesday's shooting inflamed already simmering tensions between youths and security forces in deprived urban areas, which often have large immigrant communities.
The victim was a 22-year-old man identified by the media as "Aboubakar F." who was under surveillance as part of a drug-trafficking investigation, with the policeman who pulled the trigger detained for questioning on Thursday.
Overnight, 52 cars were set alight, including the mayor's personal vehicle, while eight buildings were damaged by fire or vandalism, including a bar in a shopping centre, officials said.
There were also arson attempts on a high school and a petrol station, but no injuries were reported, with the violence only subsiding at around 6:00 am (0400 GMT).
The unrest has again highlighted tensions in deprived urban areas of France where local youths often complain about police brutality but security forces are frequently treated as targets.
In a separate development, two off-duty officers, a husband and wife, were on Wednesday night attacked in front of their three-year-old daughter in a northeastern suburb of Paris shortly after leaving a dinner party.
A police source said the attackers recognised the policewoman because she had recently stopped them for an ID check in the crime-ridden area of Aulnay-sous-Bois.
President Emmanuel Macron denounced the attack as an "appalling and cowardly act" and vowed the suspects would be "found and punished."
One of them has been arrested while the second remains on the run.
'Justice for Abou'
In a bid to defuse tensions, Prime Minister Edouard Philippe visited Nantes on Thursday where he promised "the fullest transparency" about the circumstances of the young man's death.
But there are fears the unrest could spread.
In 2005, riots erupted across the country following the deaths of two black teenagers who were electrocuted in a Paris suburb while hiding from the police.
Anger over heavy-handed policing bubbled over again last year when a young black man in another Paris suburb suffered severe anal injuries caused by a truncheon during his arrest.
Four people were arrested in Nantes overnight, including a 14-year-old carrying a petrol can and matches.
There have also been more than a dozen arrests elsewhere, including in Garges-les-Gonesse, the Paris suburb where Aboubakar F. grew up.
On Thursday evening, around 1,000 people marched in Nantes calling for "justice for Abou" and demanding clarity about the circumstances of his death.
Police said the victim was under surveillance as part of a drug-trafficking investigation and was also wanted for robbery and other offences.
They claim he resisted arrest and tried to reverse his car into a police officer.
But a witness said the car was stationary when the officer opened fire, killing the driver with a single bullet to the neck.
The riot-hit districts of Nantes all have a history of gang violence.
