The French Foreign Legion soldiers were killed north of Kabul in the Tagab valley in Kapisa province.
France has some 4,000 troops involved in Nato-led operations in Afghanistan, 72 have now lost their lives over the past decade.
Nato announced another attack on Sunday, in the south of the country, but did not give details or state the nationality of the troops.
The new deaths follow a deadly helicopter crash Saturday that killed 31 US Special Operations soldiers and seven of their Afghan counterparts in Wardak province.
Nato said Sunday it was probing the Taliban's claim that they shot down the helicopter.
Afghanistan is in the grip of a deadly insurgency launched in late 2001 by the remnants of the Taliban whose regime was toppled in a US-led invasion after the September 11 attacks.