Sixteen more members of the French armed forces were injured in the incident in the Tagab district of Kapisa province, north of Kabul.

The Afghan soldier has been arrested by the French.

President Nicolas Sarkozy said France was suspending its training programmes in Afghanistan following the attack.

According to AFP, the president said that the question of an early French withdrawal from the country is being considered.

An Afghan official told the BBC: "This is a tragic incident, a sad and tragic day for us and for Nato."

Nato confirmed in a statement that four of its troops had been killed, and that a suspect had been apprehended, but gave no further details.

Incidents of Nato soldiers being shot by their Afghan colleagues have increased in recent months.

In a separate development, a Nato helicopter has crashed in southern Afghanistan killing six troops. The nationalities of those killed has not been disclosed, but they are believed to be American.

The Taliban have claimed responsibility for that incident, but a spokesman for the International Security Assistance Force in Afghanistan said there was no enemy activity in the area at the time.

Five French soldiers were killed by a suicide bomb while on patrol in the Tagab district of Kapisa in July 2011.

French troops have been part of the Nato-led operation in Afghanistan since 2001 and currently has 3,600 troops involved in its operations there.

President Sarkozy announced in July that 1,000 troops would be withdrawn from the country by the end of 2012.

bbc.com