France, April 16 -- France has launched a national anti-terror investigation after a series of arson attacks and shootings this week targeted prisons across the country, raising fears over organised efforts to intimidate the justice system.

Officials suspect the incidents may be linked to crackdowns on narcotrafficking networks operating from inside jail cells.

In the latest incident, three vehicles were set on fire early Wednesday outside the Tarascon prison in the southern Bouches-du-Rhone region.

The fires broke out around 5.20am on a fenced car park reserved for staff, Tarascon prosecutor Laurent Gumbau told the French news agency AFP.

"One of the vehicles belonged to a prison officer, another to a company working at the detention...