The NATO-led force in Afghanistan says two of its troops are missing in the western part of the country.
The force issued a statement Friday saying the two service members went missing Wednesday while on a routine supply mission.
The statement said a search operation is under way, but did not give further details.
In a separate statement, NATO said two U.S. soldiers were killed Thursday in a roadside bomb attack in southern Afghanistan.
This year has been the deadliest for international troops in Afghanistan since the fall of the Taliban-led government in 2001.
The commander of NATO forces in Afghanistan, German General Egon Ramms, warned Thursday that international troops are running out of time in efforts to defeat the Taliban insurgency.
General Ramms said he fears that if a military stalemate develops, public support for NATO's mission will decrease even further.
On Thursday, angry Afghan villagers chanted slogans against foreign troops, protesting an overnight air strike by international forces that they say killed at least nine civilians. Local authorities said only Taliban insurgents died in the attack.
The villagers paraded the bodies of the victims in the streets of Lashkar Gah, capital of restive southern Helmand province.
The office of Afghan President Hamid Karzai publicly condemned the air strike.
The top U.S. commander in Afghanistan, Army General Stanley McChrystal, said civilian casualties are undermining the Western mission.
Some information for this report was provided by AFP and AP.
