The killings reportedly occurred at a training base shared jointly by French and Afghan forces.
Friday was among the most deadly days for French forces in the 10 years they have been serving in the international force in Afghanistan. The latest deaths bring to 82 the number of French troops killed in the Afghan campaign.
It was the latest in a series of attacks by members of the Afghan security forces, or those dressed in their uniforms, against coalition partners that have raised fears of increased Taliban infiltration of the Afghan police and army as foreign combat forces prepare to withdraw from the country by 2014.
Meanwhile, U.S. defense officials said the six soldiers killed in a helicopter crash on Thursday in Afghanistan were all U.S Marines.
There was no enemy activity reported in the area at the time of the crash.
The Associated Press contributed to this report.