A man attacked a policewoman with a knife in western France on Friday, seriously wounding her and sparking a manhunt, local police said.

The suspect, still armed, was on the run after the attack in La Chapelle-sur-Erdre near Nantes, and police dispatched 80 officers to pursue him, a police source said.

The BFMTV station said that he took the policewoman's service weapon before fleeing.

Pupils in the area's primary and middle schools were kept indoors, a city official told AFP.

A source close to the investigation said that the policewoman's injuries were life-threatening.

Interior Minister Gerald Darmanin was on his way to the scene, his ministry said.

Some 80 police are hunting the attacker
Some 80 police are hunting the attacker AFP / LOIC VENANCE

La Chapelle-sur-Erdre is a small town of 20,000 inhabitants just north of Nantes near the French Atlantic coast.

The attack came on the same day that Justice Minister Eric Dupond-Moretti called on French judges to show "firmness" when dealing with people found guilty of attacks on police forces.

All such cases of violence should go before a criminal court, he said in a memo to investigating magistrates seen by AFP.

French police officers have demanded better protection and harsher punishment for attacks against them.

Earlier this month, officer Eric Masson was shot dead while investigating activity at a known drug-dealing site in the southern city of Avignon.

Masson's death came after the April 23 killing of Stephanie Monferme, a police employee who was stabbed to death in the town of Rambouillet outside Paris in the latest jihadist attack in France.