The latest attack comes amid an upsurge in Taliban activity.
On Friday, a suicide bomb attack in southern Afghanistan killed at least six people, said a provincial governor.
Ghulam Dastagir Azad, governor of Nimroz province, said the bomber was on foot and apparently targeted a police official who was out shopping. Azad said the blast destroyed four shops and killed the police official and at least five civilians.
Last year saw the death of 151 US troops in Afghanistan, the highest toll since the 2001 invasion to oust the Taliban.
There were 1,160 civilians killed in incidents in 2008, according to an AP casualty count - 368 by foreign and Afghan troops and 768 by the Taliban.
In a statement on Thursday, Hamid Karzai, the Afghan president, said 17 civilians were killed during clashes between US-led troops and Taliban fighters in the eastern Laghman province on Tuesday.
Karzai blamed the "terrorists" for using civilians as human shields in their battles with foreign troops, but he also criticised international forces for engaging fighters in villages.
But the US military said all those killed in Tuesday's battle were fighters.
"We held [a meeting] with local government officials after the operation, and all local Afghan leaders confirmed that all 32 killed in this operation were hostile militants," Colonel Jerry O'Hara, a US military spokesman, said.