A 15-year-old boy's hand was blown off during a confrontation between police and demonstrators near a school in France, an official has said, as student protests continue across the country.

The "very serious incident" happened in the north-eastern city of Lens on Monday morning, according to the prefect of Pas-de-Calais, François-Xavier Lauch.

"The student's life is not in danger," he said, adding that the teenager was transferred "very quickly" to a hospital nearby.

Around 500 schools were partially or totally closed across the country on Monday amid student protests over the condition of school buildings and staffing which have led to clashes with police in recent days.