At least four Eritrean refugees are in critical condition after being shot during a mass brawl between some 130 Afghans and Eritreans in the northern French city of Calais, local media outlets reported.
The fighting started while volunteers were handing out food to refugees but later spread to other locations in the city, according to Le Monde newspaper.
Officials said a further 22 people suffered wounds, including two police officers trying to break up the fighting, which involved more than 100 Eritreans and around 20 Afghans.
Speaking to police officers on Thursday evening, French Interior Minister Gerrard Collomb described the violence as "exceptionally serious" and promised that those responsible would be punished.
Collomb also ordered the deployment of more police officers to the area to avoid a repeat of the events.
Calais was home to the unofficial "jungle" refugee camp, which housed thousands of refugees in tents, until French authorities demolished it in October 2016.
The city and neighbouring areas drew refugees and migrants from around the world due to its proximity to England, which lies at the other end of a 25-mile stretch of sea.
According to local authorities, up to 800 refugees and migrants remain in Calais.
The wider Calais region has experienced previous incidents of violence, including clashes between rival human trafficking gangs.
Mass brawls between refugees have also broken out occasionally.