NATO military commanders will beef up security measures to prevent insurgents from infiltrating the Afghan army after French troops were killed by a renegade soldier, the alliance chief said Friday.

NATO defence ministers endorsed a French proposal to task military authorities with devising new plans before the end of the month as they wrapped up two days of talks focused on the decade-old war.

"We have already taken a lot of steps," NATO Secretary General Anders Fogh Rasmussen told a news conference. "But in light of recent events we agreed to strengthen those efforts."

Six percent of overall NATO deaths in Afghanistan have been attributed to attacks by Afghan security forces, according to a confidential alliance report leaked to the media last month.

Some 130,000 NATO troops work with more than 300,000 Afghan security forces.

"There is a realisation about the need to better control the recruitment to prevent infiltrations in the army," French Defence Minister Gerard Longuet told reporters.

"These events are rare but they are symbolically important for the credibility of the Afghan army," he said. "Quantitatively, they are marginal. Media-wise, they are unbearable."

NATO did not provide details about the plans but they are expected to focus on better controlling the recruitment of Afghans, deeper investigations into potential recruits and the use of biometric technology.

The killing of four French unarmed soldiers at the hands of an Afghan they were training last month prompted French President Nicolas Sarkozy to end his country's combat role in Afghanistan by the end of 2013.

France will gradually withdraw its 3,600 troops, eventually leaving behind around 400-500 military trainers at the end of 2014, when NATO is scheduled to end its combat mission, Longuet said.