Interior Minister Massaoudou Hassoumi said a policeman and three civilians died in yesterday's disturbances in Zinder in which three churches were ransacked and the French cultural centre was burned down.
Thousands of protesters gathered outside mosques after Friday prayers to vent anger at the depiction of the prophet, which is considered taboo to most Muslims.
Twenty-two members of the security forces and 23 protesters were hurt in the ensuing clashes, national radio reported, as one Catholic and two Protestant churches were attacked.
Twelve people, including some of France's best-loved cartoonists, died in a jihadi attack on the satirical magazine's Paris offices last week.