Nicolas Sarkozy announces the suspension of France's training programme in Afghanistan. Reuters

France is suspending military training operations in Afghanistan and considering whether to withdraw its entire force early after four French soldiers were killed by an Afghan soldier in the Taghab valley of eastern Kapisa province.

The shootings on Friday were the latest of several in which western soldiers have been killed by members of the Afghan security forces, undermining trust in the runup to the withdrawal of foreign combat troops in 2014.

The French president, Nicolas Sarkozy, announced that France would temporarily stop all its training operations and co-operation with Afghan troops. He immediately dispatched the French defence minister, Gerard Longuet, to Afghanistan to establish whether "conditions were safe" for French soldiers. He said if safe conditions were not clearly established France would consider an early withdrawal of all its troops from Afghanistan.

"If the conditions of security are not clearly restored, then the question of an early withdrawal of the French army would arise," Sarkozy said.

"The French army is in Afghanistan at the service of the Afghans against terrorism and against the Taliban. The French army is not in Afghanistan so that Afghan soldiers can shoot at them," he added.

The French foreign minister, Alain Juppé, later said that while four French soldiers were killed, 15 more were wounded, eight of them seriously. He said "our soldiers are in Afghanistan to help the Afghan people and the Afghan army in their fight for freedom and democracy. It is incomprehensible and unacceptable that soldiers in the Afghan army murder French soldiers."

He brushed aside the question that the issue of troops in Afghanistan might be being used for electoral purposes, three months before Sarkozy stands for re-election, saying the soldiers' deaths were "a tragedy".

He said France now wanted "credible assurance" from the Afghan government that it had stepped up security in its recruitment process to the Afghan army and that French troops were safe. If not, France would consider pulling troops out early.

A total of 82 French soldiers have died in Afghanistan since the start of the conflict in 2001. There are currently 3,600 French troops in the country and a large part of their role is training the Afghan army.