Two US soldiers and their Afghan interpreter were killed on Saturday when the vehicle they were travelling in struck an "improvised explosive device" in south Afghanistan, a statement issued by the US-led military said.
A third soldier was wounded in the blast in Ghazni province, around 260km south-west of Kabul, the statement said.
The wounded soldier was flown to Kandahar Airfield hospital and was in a stable condition, it added.
Some 20,000 US-led troops are stationed in Afghanistan hunting for the remnants of Taleban and al Qaeda, including Osama bin Laden. More than 60 US military personnel have died in conflict in Afghanistan since the Taleban were driven from power in late 2001.
A band of Taleban fighters attacked a small convoy of election workers in central Uruzgan province, killing at least two people, officials said on Saturday.
Uruzgan Governor Jan Mohammad Khan told Reuters the Taleban attacked the election workers on Friday evening as they left Charchino district to register voters at another district.
"A group comprising at least 70 to 80 Taleban attacked their four vehicles, killing two registration team officers."
Afghan forces hunted for the assailants in the rugged mountains, but no arrest have been made so far, he said. A Taleban spokesman claimed responsibility for the attack in Uruzgan, around 350 km, south-west of Kabul.