Northern Ireland fans were drawn into fighting in Nice on Saturday night as European Championship violence spread, witnesses said.
According to a Northern Ireland police officer accompanying fans at the scene, French riot police moved in after local Nice youths hurled bottles at Northern Ireland supporters in cafes near the central Place Massena.
"About 20 to 30 Nice youths started throwing bottles at the Northern Ireland fans. Some bottles were thrown back, some punches were thrown," the officer said.
"French police arrived to contain the situation."
Dozens of riot police were on the pedestrian street after the incidents ended.
Northern Ireland play Poland in Group C in Nice on Sunday. There are an estimated 10,000 Northern Ireland fans and several thousand Polish in the city for the game.
Christian Estrosi, president of the regional council taking in Nice, "condemned" the violence in a Twitter statement.
Earlier, hundreds of English and Russian fans fought pitched battles in the streets of Marseille ahead of their countries' opening match, leaving two English supporters in a critical condition in hospital.