Several prisons in France have been hit by a wave of overnight attacks, according to the country's authorities.

Vehicles were set on fire in prison car parks, and one prison entrance was targeted with gunfire from an automatic weapon.

Justice Minister Gérald Darmanin said prisons had faced "intimidation attempts" and linked the attacks to the government's crackdown on drug trafficking.

Seven establishments were attacked, according to the Parisien newspaper: in Toulon, Aix-En-Provence, Marseille, Valence and Nîmes in southern France, and in Villepinte and Nanterre, near Paris.

In a post on X, Darmanin said he was travelling to Toulon to offer his support to affected officers.

Without directly attributing blame for the attacks, he said the French government was "facing up to the problem of drug trafficking" and taking measures that would "profoundly disrupt" criminal networks.

Interior Minister Bruno Retailleau said the government's response must be "relentless".

"Those who attack prisons and officers deserve to be locked up in those prisons and monitored by those officers," he posted on X.

He added that he had instructed police to immediately strengthen security at prison facilities.

The prison guard union, FO Justice, expressed its "deepest concern and anger" following the "extremely serious" attacks overnight.

The union posted updates from the aftermath of several attacks on X, including images of burnt-out vehicles in prison car parks and bullet holes in the Toulon prison entrance gate.

It called for urgent government action to protect prison staff.

Monday night's attacks come after seven vehicles were set on fire in a similar attack on France's national school of prison administration on Sunday, according to the union.

"It is worrying to note that some people no longer hesitate to directly attack the prison's property, a symbol of state authority," it said in a statement.

No group has claimed responsibility for the attacks, but La Parisien reports that the letters DDPF - meaning "French prisoners' rights" - were found inscribed on damaged vehicles. The AFP news agency says anarchist slogans were found at some sites.

AFP quotes a source close to the case as saying the attacks appeared to be coordinated and "clearly linked" to the government's strategy against drug trafficking.

A law is passing through the French parliament which creates a special prosecutor's office to deal with drugs crime, with new powers for investigators.