The suicide attack was similar to scores of others in Afghanistan that are mostly claimed by extremist Taliban fighters waging an insurgency against the government, which is backed by about 70,000 foreign soldiers.
The attacker detonated an explosives-filled vehicle outside the city of Jalalabad as it approached a convoy of US soldiers, provincial government spokesman Ahmad Zia Abdulzai told AFP.
"Six civilians were wounded including two children but there was no harm to the American forces," Abdulzai said. One of the children was in a critical condition, he said. He said that another US-led military convoy had accidentally killed a municipal worker in the same area when it knocked the worker off his bicycle.
The US-led coalition, which remained after the invasion to round up Taliban, al Qaeda and other rebels, announced separately that it had killed four alleged militants in the southern province of Kandahar early Sunday. Afghanistan's insurgency has been increasing steadily, last year recording the highest number of attacks which the United Nations says accounted for most of nearly 2,200 civilian deaths in 2008.