The bomber, thought to be a member of the Taliban, detonated a car packed with explosives in Afghanistan, killing three government soldiers and wounding three, police said on Thursday.
The attack occurred at a checkpoint in the southeastern province of Khost on Wednesday when Afghan soldiers and US troops were checking vehicles, a police official said.
Mohammad Zaman, a senior provincial police official, told reporters that apart from the suicide bomber, three national army soldiers were also killed in the attack.
But Mohammed Ayub, the regional police chief, said three soldiers, the driver of the vehicle and a farmer working nearby were killed along with the bomber.
It was not clear whether the driver was an associate of the assailant or an innocent victim. Three soldiers were wounded, as well as a second farmer.
The attacker was sitting in the back seat of the vehicle and detonated explosives hidden under a woman's burqa shroud when soldiers asked to see his ID, the police chief said
There were no casualties among the US troops, he said.
The Pakistan-based Afghan Islamic Press said, Mullah Abdul Samad, a Taliban commander in Khost, claimed responsibility for the attack.
Wave of attacks
Dozens of people, most of them civilians, have been killed in a wave of attacks - including 14 suicide bombings - across Afghanistan's south and east in recent months.
The Nato-led force is expanding
its presence in Afghanistan
The Taliban, fighting US-led and government troops since it was ousted in late 2001, have claimed responsibility for most of the violence and say they will continue their insurgency until foreign troops withdraw.
The government says the Taliban and their al-Qaida allies are trying to scare off Nato members from contributing troops for an expansion of a Nato-led peacekeeping force, while the United States begins to trim the number of its troops in a separate force battling the insurgents.
The Dutch parliament is set to vote on Thursday on whether to send more troops for the Nato force.
The Nato supporter and US ally delayed its decision last year to send up to 1400 troops, threatening the expansion plan.
The United States has more than 18,000 troops in Afghanistan battling Taliban and al-Qaida militants and hunting for their leaders.
Under the expansion plan, the 9000-strong Nato-led force is due to get about 6000 more troops and move into the dangerous south this year.
Most Afghans say foreign troops are the only way to ensure security until Afghanistan's own security forces are built up.