At least two NATO soldiers were killed in an ambush on Tuesday in southern Afghanistan, a day after the alliance took control of security in the volatile region.
The soldiers were part of a patrol that was attacked by insurgents armed with rocket-propelled grenades in Helmand province, a statement by the International Assistance Security Force (ISAF) said.
"Two ISAF soldiers were killed in this attack, one wounded and one remains unaccounted for," it said.
The statement did not give identity of the victims.
Taliban guerrillas and drug barons have been operating for years in Helmand, the main drug producing region of Afghanistan which is the world's leading supplier of heroin.
On Monday, NATO forces took over security in the Afghan south from the U.S. led coalition to begin one of the biggest ground operations in the alliance's history.
More than 1,700 people have been killed in Taliban-led insurgency, attacks by drug barons and operations of U.S.-led forces this year, mostly in Afghanistan's southern areas.
Most of the victims were militants, according to Afghan and coalition forces, but the toll also includes over 70 foreign troops.
The violence is the bloodiest since coalition overthrew Taliban's government in 2001.
NATO peacekeeping troops, mostly from Britain, Canada and the Netherlands, have been taking up positions in the south for the past few months and have already been engaged in heavy fighting with Taliban guerrillas, in some cases allied with drug runners.
The move should allow the U.S. army to trim down the size of its force from 23,000 to 20,000 and NATO is expected to expand its mission later this year into the east where the militants are active too.