The agency quoted military officials on Thursday as saying five US special forces were wounded in the fighting in the Uzbeen Valley.
Uzbeen Valley is a Taliban stronghold where 10 French soldiers were killed in an ambush in August 2008.
The operation, codenamed "Septentrion", was aimed at "reaffirming the sovereignty of Afghan security forces in the north of the Uzbeen Valley", said Colonel Benoit Durieux of the French Foreign Legion.
Septentrion comes weeks after Barack Obama, the US president, announced he was sending 30,000 extra troops to Afghanistan, but also said they would begin to pull out by mid-2011.
General Stanley McChrystal, the commander of US and Nato forces in Afghanistan, told Afghan members of parliament recently that there would be "significant improvements in security" by the middle of next year.