"Firearms! Can it be considered normal that people turn firearms on police?"

President Francois Hollande said the state would "mobilize all its resources to combat this violence", which has shaken depressed quarters of major French cities at regular intervals in the past decade.

Unrest is often blamed on a combination of poor job prospects, racial discrimination, a widespread sense of alienation from mainstream society and perceived hostile policing.

Interior Minister Manuel Valls was met by a crowd of about 100 young men when he arrived in Amiens to discuss two nights of violence apparently sparked by tension over spot police checks on residents.

"Calm down! Calm down!" Valls yelled as the crowd jostled him while he entered the town hall surrounded by bodyguards.

Read More | "French youths jostle minister after riot overnight" | John Irish and Pascal Rossignol | ?Reuters | ?@lolprol