Paris: French Justice Minister Gerald Darmanin said on Tuesday that several prisons in France were attacked overnight.
He said the attacks seemed to be linked to government efforts to clamp down on drug trafficking.
Darmanin said that prisons were being targeted with fire and even heavy weapons.
"Prisons are facing intimidation attempts ranging from vehicle burning to automatic weapon fire," he posted on social media.
Several facilities were attacked during the night into Tuesday, with officials saying that Toulon-La Farlede was targeted with heavy gunfire.
"I am travelling to Toulon to support the officers involved," Darmanin said.
"The Republic is facing drug trafficking and is taking measures that will profoundly disrupt criminal networks. It [France] is challenged and will be firm and courageous."
According to a statement from the prison union FO Justice, "vehicles were burned, entrance doors set on fire, and even targeted by heavy weapons fire."
At the Villepinte remand center in the Paris region, closed circuit footage showed two perpetrators entering the facility via an earth mound, each setting fire to a vehicle, with a third being damaged by the spread of the fire.
Police sources said vehicles were also set alight at facilities in Nanterre near Paris and the two southeastern prisons of Aix-Luynes and Valence.
At Toulon-La Farlede, 15 impacts were recorded on the facility's door after a "heavy weapon attack, Kalashnikov-style."
From Sunday night into Monday, fires were also set in the parking lot of the National School of Penitentiary Administration (ENAP) and Raau prison in the Paris region.
What prison unions are saying
"These criminal acts are a frontal attack against our institution, against the Republic, and against the officers who serve it daily," FO Justice said.
The union demanded "a strong, immediate, and unambiguous response from the state."
Another union, UFAP Unsa Justice, told the AFP news agency that the prison administration did not have "the human resources to ensure 24-hour security around the facilities."
Since his appointment, Darmanin has expressed his desire to isolate France's 100 biggest drug traffickers in a high-security prison.
The French parliament is also currently reviewing a law to "free France from the trap of drug trafficking," which includes the creation of a National Prosecutor's Office for Organised Crime (PNACO).