A suicide attacker blew himself up near international troops in the southern Afghan town of Qalat early Thursday, wounding four civilians, police said.
The bomber ran at a patrol in the centre of the town, capital of Zabul province, and detonated the explosives he was carrying, Deputy Police Chief Faridullah Khan told AFP.
The international troops suffered no casualties but four civilians, young men, were wounded, he said from the town which is about 400 kilometres (250 miles) south of Kabul.
The media office for the multinational NATO-led International Security Assistance Force, which has US and Romanian soldiers in Qalat, could not immediately confirm the explosion.
No one immediately claimed responsibility but the attack was similar to scores of others carried out by the extremist Taliban movement, which makes heavy use of bombings in an insurgency against the Western-backed government.
There were two suicide bombings in the country on Wednesday, one aimed at Canadian troops in the south that killed a child and the other outside a district government in the east that killed one person and wounded several.