French authorities have announced plans to ban social media for those under the age of 15 and the sale of knives to minors after the murder of a teaching assistant by a 14-year-old boy plunged the country into shock.

A secondary school pupil was arrested on Tuesday after killing a 31-year-old school assistant with a knife during a bag search in Nogent in eastern France.

Friends and well-wishers left flowers and messages of support in front of the secondary school struck by the tragedy.