A 15-year-old boy killed a fellow pupil and wounded three others in a stabbing attack at a high school in the western French city of Nantes on Thursday before he was overpowered by teachers, police said.

The motive was unclear for the attack, which occurred at a time of heightened concern in France about knife attacks in schools.

Armed French officers were seen outside the school on Thursday after four students were stabbed A teenage girl has been killed and three students were injured in a stabbing at a private school in western France.