A manhunt was underway Wednesday in southern France for a man who shot dead his boss and a colleague at a sawmill in the mountainous Cevennes region before escaping into a forest.

Around 300 officers joined the search for the 29-year-old suspect, who is accused of shooting his boss in the head shortly after arriving for work on Tuesday morning and then killing a work colleague before fleeing into the woods.

The local public prosecutor, Eric Maurel, on Wednesday urged the man to turn himself in.

"I'm calling on him to listen to reason, lay down arms and explain what spurred him to act as part of a peaceful surrender," Maurel told reporters.

An employee of the sawmill, who witnessed the killings in the village of Les Plantiers, told investigators the shooter pulled a gun after he was chided for not saying hello on arriving for work.

Around 300 police officers joined the search for the 29-year-old suspect in the remote Cevennes region
Around 300 police officers joined the search for the 29-year-old suspect in the remote Cevennes region AFP / CLEMENT MAHOUDEAU

Stunned by the attack, another colleague tried to intervene, but the suspect also shot him in the head, the witness said.

Investigators said the man had recently clashed with his boss about his working hours.

Police backed by helicopters continued Wednesday to comb the cave-studded mountains for the suspect, described as a keen hunter who had at one point talked of becoming an army sniper.

The rugged Cevennes, a bastion of French Protestantism situated north of Montpellier, is one of the most remote regions of France.

Numerous French Resistance members hid out in the area's caves and forests during World War II.