French police in the southern city of Montpellier sought the driver who struck and killed a 14-year-old boy celebrating France’s World Cup victory before fleeing the scene.
Video on social media showed a white hatchback surrounded by fans which speeds away when someone tears down a flag hanging out of its rear window.
“The driver violently left the line of cars and hit a 14-year-old boy,” who later died of his injuries at a hospital, the local prosecutors’ office said.
The car was found abandoned nearby, and the police investigation is “progressing rapidly”, it said.
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The tragedy marred France’s victory over Morocco to reach the championship’s finals, with most celebrations across the country good-natured though with scattered incidents of unrest.
“Aymen’s death has plunged us into a terrifying ordeal,” the boy’s family said in a statement published at its request by city authorities in Montpellier.
“We call for complete calm and express our confidence in the police and judiciary,” it said.
The accident occurred in the Paillade district, one of the poorer areas of Montpellier, whose Mayor Michael Delafosse tweeted that he hoped “the people who carried out this awful act are found and put on trial”.
Local MP Nathalie Oziol expressed “immense sadness, a sporting event ends in absolute tragedy”.
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Around 10,000 police were deployed across France for the match, as authorities worried about possible tensions between French supporters and those backing its former North African colony.
Around 100 arrests were made in and around Paris before 1:00 am on Thursday, police said, and dozens of others were detained in cities including Lyon and Avignon.