France on Friday threatened to accelerate its withdrawal from Afghanistan, after an Afghan soldier shot and killed four French troops.

President Nicolas Sarkozy suspended military operations in Afghanistan and said he is considering an early pullout of French troops if security conditions “are not clearly established,” following Friday's attack.

Fifteen French troops were wounded in the same assault that occurred in the Taghab district of Afghanistan's eastern Kapisa province.

French Defense Minister Gerard Longuet said the French troops were unarmed when the attacker opened fire during a training exercise at a base jointly operated by French and Afghan forces. The shooter has been apprehended.

Friday's incident is the latest of several attacks in which international troops have been killed by Afghan security forces.

In December, an Afghan soldier opened fire and killed two members of the French Foreign Legion in Kapisa. And earlier this month, an Afghan soldier shot and killed an American service member in Zabul province.

Friday's deaths bring the number of French troops killed in the Afghan war to 82. France has about 3,600 soldiers serving in Afghanistan, mainly in the east, with all French combat troops scheduled to leave the country in 2014.

President Sarkozy said Friday that it was “unacceptable” that Afghan troops would attack French soldiers. He said Defense Minister Longuet and France's army chief of staff are traveling to Kabul Friday to determine the circumstances behind the attack and will report back on how to proceed.

Afghan President Hamid Karzai expressed his condolences for Friday's attack. He noted that France and Afghanistan have enjoyed a “sincere” relationship in which France has provided “extensive” help to Afghanistan over the last decade.

In Latvia, NATO Secretary-General Anders Fogh Rasmussen said it was a “sad day” for international troops in Afghanistan and the French people, but insisted such incidents are “isolated.”

A Taliban spokesman praised the attacker but did not claim responsibility for the shooting in Kapisa.

The White House said Friday its thoughts and prayers were with the French people and that French forces served with “valor and honor” in Afghanistan. Spokesman Jay Carney would not comment on President Sarkozy's remarks about a possible early withdrawal.

The New York Times on Friday cited a classified coalition report, which says such attacks are motivated by deep-seated animosity between the forces that are supposed to be allied. The report says ill will and mistrust run deep among civilians and militaries on both sides.

But NATO spokesman U.S. Lieutenant General Jimmie Cummings, Jr. said Friday that incidents where Afghan soldiers have wounded or killed coalition members are isolated cases and are “not occurring on a routine basis.”

Cummings added “we train and are partnered with Afghan personnel every day and are not seeing any issues or concerns with our relationships.”

Meanwhile late Thursday, a coalition helicopter crashed in the southern Afghan province of Helmand, killing six U.S. Marines.

A NATO spokesman said there was no insurgent activity reported in the area when the helicopter went down.

The coalition is investigating the crash, the worst since August of last year when 30 American service members were killed after their helicopter was shot down by militants in Wardak province.