The attack happened Thursday night in Shahra Safa in Zabul province, said Muhammed Jan Rasolyar, the provincial governor's spokesman. Taliban spokesman Qari Yousef Ahmadi claimed responsibility.
Insurgents have intensified attacks on NATO supply convoys in Afghanistan and neighboring Pakistan, where one of the alliance's vital supply lines begins.
The violence recently resulted in the route's temporary closure. NATO helicopters pursuing militants mistakenly shot three Pakistani soldiers at a border post, prompting Pakistan to shut the supply route. It was reopened after American officials issued public apologies.
In another border area, a roadside bomb killed a district chief and two colleagues traveling in Dur Baba, in eastern Nangarhar province near the Pakistani border, the Afghan government said.
NATO forces and the Afghan army are pushing into the insurgency's traditional heartland in the south. Residents say there are pockets of improved security but Taliban attacks have increased in other parts of the country.
In Jaji Maidan district in the eastern province of Khost, around 200 demonstrators protested alleged rigging in parliamentary elections held Sept. 18. They said no results had been announced for their district.
Afghan officials threw out nearly a quarter of ballots cast because of fraud. The polls were seen as a crucial test for the government after last year's fraud-marred presidential election. This time officials indicated there was widespread cheating, but also appeared to be more active in excluding fraudulent ballots.
