A suicide bombing attack injured two U.S. engineers and two Afghans on Sunday on the eastern outskirts of Kabul, capital of Afghanistan.
A Xinhua journalist at the site saw several U.S. Humvee vehicles were staying there, and some U.S. soldiers carrying machineguns had condoned off the spot. Some shattered glass were scattering at the site.
A witness said an attacker belted with explosives rushed to a white car at around 2:45 p.m. local time, and blew himself up, injuring two U.S. engineers and two Afghans in the car.
An official with Afghan Interior Ministry, who refused to name himself, confirmed the casualties with Xinhua.
The official said, the enemies of Afghanistan, a term used to refer to the Taliban, was behind the attack.
The engineers had been constructing a jail nearby for the Afghan government to keep suspected militants and those released by the U.S. military from the Guantanamo Bay of Cuba.
The U.S. government agreed months ago to hand over all Afghan detainees at the Guantanamo Bay back to this country.
Also on Sunday, a suicide car bombing killed one civilian and wounded four others, some of whom were in serious condition, in the southern Kandahar province.
The attack occurred at around 9:20 a.m. local time in Mirwais Mina area of Kandahar city, the provincial capital.
The attacker was killed in the explosion, which apparently was targeting a Canadian military convoy passing by.
A total of 173 persons had been killed by suicide bombings in Afghanistan this year, and 151 of them were Afghan civilians, NATO troops said on Wednesday.
Due to rising Taliban-linked insurgence this year, Afghanistan has plunged into the worst spate of violence since the Taliban regime was toppled in late 2001.
Over 23,00 persons, mostly Taliban rebels, were killed in this Central Asian country in the past nine months.