A roadside bomb killed eight U.S. troops in southern Afghanistan Thursday, the U.S. military told Reuters.
The attack was the deadliest single attack on foreign troops in a month.
Another NATO service member was killed in a helicopter crash in Afghanistan's east earlier Thursday, the Los Angeles Times reports. The crash was under investigation.
Afghanistan has seen a fresh wave of violence as Taliban forces carry out their so-called spring offensive.
Targeted strikes by U.S. forces have weakened the Taliban and other militant groups over the past year, but they manage to still threaten NATO troops with bombs and improvised explosive devices, the Los Angeles Times states.
The bombing comes one month after an Afghan air force pilot shot dead eight U.S. service personnel and a U.S. contractor in Kabul, Reuters states.
Foreign troops are to start a reduction of forces this summer, but critics of the war argue a pullout should be accelerated, particularly as a result of the killing of Al Qaeda leader Osama bin Laden on May 2.
More than 1,580 of the 2,480 foreign troops killed in Afghanistan since the war began in 2001 have been Americans.