Hundreds of students are barricading school entrances across Paris and demonstrating in protests against alleged police brutality, just as a major union of police officers staged its own rally to demand more personnel and equipment.

The separate demonstrations on Thursday come three weeks after a young environmentalist died during a protest in southern France in which several hundred activists opposed to a dam project clashed with police.

An investigation is continuing into the death of Remi Fraisse, but an autopsy found a large wound on his back was caused by some kind of explosion.

Students stacked trash cans before doors at several Paris high schools, as about 150 students marched from the Place de la Nation. The Alliance police union was leading its demonstration at nearby Place de la Bastille.