The fans gathered in the northern French city after Lille won at Angers to clinch the title in their last game of the season on Sunday night.
“The police had to make seven arrests, including one for ‘attempted homicide against the police using a vehicle’,” the prefecture said.
Three people were arrested for throwing projectiles, two for burning rubbish bins and one for possession of fireworks, it added.
Twenty people were treated by emergency services, including three who needed to be taken to hospital, the statement said.
The police had set up a roadblock to control entry to the Grand-Place, the historic centre of the city, but supporters gathered anyway and were allowed to make their way into the square through side streets.
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They waved flags and scarves in their team’s colours, in a red halo of smoke, to the sound of exploding firecrackers while singing “We are the
champions” and “Freed from desire” and dancing.
The mood was generally festive and good-natured atmosphere. On Saturday, the regional prefect Michel Lalande had called on the people of Lille to “enjoy this moment of sport in complete safety, in a health context that is improving but remains fragile”.
He asked “everyone to continue to respect all the health measures in force and not to set off fireworks on the public highway”.