A judge will investigate the killing of 10 French soldiers in a 2008 ambush in Afghanistan after their families accused military commanders of negligence, a French appeals court ruled on Monday.

The court said investigating judge Frederic Digne could continue his probe, opened last year, after prosecutors had appealed against the investigation.

The families filed a civil complaint for "endangering lives" and "failing to prevent a crime" over the ambush, which saw 10 soldiers killed and 21 wounded after Taliban guerrillas ambushed a patrol in Uzbin, east of Kabul.

Media reports have quoted classified French and NATO documents that concluded the soldiers were poorly equipped and ill-organised. French authorities have denied this.

"This is a relief because, through the prosecutor's office, the state had been doing everything possible for this investigation not to be opened," said Gilbert Collard, a lawyer for the family of one of the dead soldiers.

"We had to fight, but we will finally know how these young soldiers were killed, how they were sacrificed."

Collard said he would call for a number of witnesses to be questioned and for a classified report into the ambush to be made public.

The ambush saw Taliban fighters attack a convoy of about 100 NATO soldiers, mainly French, on patrol in a mountain pass and pin them down with machine-gun, sniper and mortar fire.

NATO forces managed to regain control of the area after a nine-hour battle and the arrival of reinforcements.

Media have quoted both French and NATO reports saying the soldiers lacked ammunition and communication equipment. Reports have also cited a lack of air reconnaissance and surveillance.

In their complaint, the families claimed the soldiers suffered from "a clear lack of means" and that "some officers were not up to their mission".

"We have never said that a soldier does not face his possible death when he puts on a uniform," Collard said.

"But we have always said that no one has the right to send soldiers to their death without giving them the means to defend themselves, without giving them the means to escape from a trap created by negligence and by carelessness."

France's defence ministry has previously raised concerns that the judicial probe would open the door to legal action being taken in other cases of military losses.

Reacting to Monday's decision, Defence Minister Gerard Longuet said he would study the ruling but appeared to suggest that the conduct of military operations should not be subject to legal challenge.

"The army is subject to the law, so it is normal that it gives an account. However, it has always been recognised that the conduct of operations is a unique exercise," he said on France Inter radio.

At the time the ambush marked the deadliest attack on NATO forces in Afghanistan since the fall of the Taliban at the end of 2001.

The court's ruling came as France prepares to draw down its presence in Afghanistan and after recent deadly attacks on French troops, including the killing earlier this month of four French servicemen by a renegade Afghan soldier.

President Nicolas Sarkozy announced Friday that France would be withdrawing its 3,600-strong contingent from Afghanistan by the end of 2013, a year before the international deadline of 2014.

A total of 82 French troops have been killed in Afghanistan since the start of their deployment in 2001.