France threatened on Friday to pull out early from the Nato-led war in Afghanistan after a rogue Afghan soldier opened fire on French soldiers, killing four and wounding about 15 others.
The killings in the Taghab valley of Afghanistan's eastern Kapisa province were the latest in a series of incidents in which Afghan troops have turned on Western allies.
French President Nicolas Sarkozy said all French operations on the ground were being suspended and his defence minister was dispatched to Afghanistan to clarify the situation.
"If the security conditions are not clearly established then the question of an early return of French forces from Afghanistan will arise," said Sarkozy.
France has almost 4,000 troops in Afghanistan as part of the 130,000-strong Nato-led force there. French troops mainly patrol Kapisa, a mountainous province near Kabul. They are due to leave by around the end of 2013.
Nato said four soldiers were killed. French Foreign Minister Alain Juppe told a news conference about 15 others were wounded, eight of them seriously.
The Taliban did not claim responsibility for the attack, but told Reuters that an Afghan soldier had killed eight French troops. The Islamist group often exaggerates accounts of engagements with foreign forces and casualties.
Nato has been rapidly expanding the Afghan security forces so that they will be able to take over all responsibility for security when Western combat forces leave in 2014.
Previous incidents in which Western troops were killed by Afghan colleagues have been blamed either on Taliban infiltration of the Afghan military, or on stress, indiscipline and divided loyalties within the hastily trained Afghan ranks.
"It is incomprehensible and unacceptable that Afghan army soldiers assassinate French troops," Juppe told reporters.
Afghan President Hamid Karzai, who is due in Paris on Jan. 27 to sign a cooperation treaty, expressed his "deep sadness and condolences to the families of the victims".
The Taliban "has skilfully placed the Taliban inside enemy ranks who have carried out attacks, however it is not clear whether the shooter belonged to the Emirate", spokesman Zabihullah Mujahid said in an emailed statement, using another name that the Taliban use for themselves.
Insurgent Maulvi Jamilur Rahman, who identified himself to Reuters as Taliban commander of Kapisa, said the Afghan soldier had been in contact with his fighters. "Now we are in control of a major portion of the area," Rahman said.
Karim Pakzad, associate researcher at the French Institute for Strategic Relations in Paris, said the move by Sarkozy was playing into the Taliban's hands.
"The Taliban are stronger than ever and want to impose their conditions on negotiations, and these attacks are a way to accelerate the departure of Nato troops," he said.
Jimmie Cummings, spokesman for the NATO-led International Security Assistance Force in Kabul, said: "There is no indication that these incidents are linked or part of any larger coordinated effort."