Around 100 French youths have clashed with police in the northern city of Amiens, shooting at officers and setting cars, a leisure centre and a nursery school ablaze.
Police reinforcements have been dispatched and Interior Minister Manuel Valls is due to visit the city, where two nights of violence were apparently sparked by tension over spot police checks on residents.
"Sixteen police were injured, some by buckshot fire," Thomas Lavielle, an official at the prefect's office in the region, told a local television station.
The Amiens suburb which erupted in violence has already been identified as needing extra policing by Mr Valls' Socialist government.
French President Francois Hollande said his government would do all that was needed to ensure law and order in Amiens.
"Our priority is security, which means that the next budget will include additional resources for the gendarmerie and the police," he said.
Tensions remain high in France's rundown suburbs, where poor job prospects, racial discrimination, a widespread sense of alienation from mainstream society and perceived hostile policing have periodically touched off violence.
Weeks of rioting in 2005, the worst urban unrest in France in 40 years, led to the imposition of a state of emergency by the then centre-right government.
The violence provoked months of agonised debate over the state of the grim housing estates that ring many French cities and the integration of millions of black and North African immigrants.
The death of two youths hit by a police car sparked violence in 2007. More unrest followed in 2010, when police shot and killed a youth who had robbed a casino.