Around 200 detonators and grenades have been stolen from a military site in southern France, according to officials.

Police investigating the case believe the munitions were stolen overnight at the Mirimas site, which is run by a combination of military services west of Marseille.

Thieves appear to have cut through a fence to enter the high-security site, according to a police official who spoke to The Associated Press on a condition of anonymity.

Defense Minister Jean-Yves Le Drian has ordered an investigation to be launched into who carried out the break-in, and how it was organised.

A poster at the military base reads "protected area, do not enter without authorization" in Miramas (Image: Claude Paris/AP)

He also tasked a government office with putting forward "corrective measures" of how such sites are protected within 15 days.

Some nine storehouses were targeted in the theft, which was a first for the site, Mayor Frederic Vigouroux of Miramas told The Associated Press.

"It wasn't cotton candy that was stolen,” he said. "These are dangerous munitions."

Around 160 civilians and soldiers work on the site each day, where guards accompanied by sniffer dogs patrol behind two fences which are separated by a “no-man’s-land”-style area, according to French military spokesman Col. Gilles Jaron.

He added that as the explosives are not specialty munitions, they are relatively easy to use.

The 200-hectare (500-acre) base sits on the outskirts of the town of 30,000 and stocks munitions like those used in French military operations in Mali and Afghanistan.