A governor for the Uruzgan province, Jan Muhammad, said Taliban fighters came down from mountain hideouts and killed the four government militiamen.
"Four of our soldiers were killed on Monday by Taliban in the locality of Charchino," Muhammad said. He was speaking from the provincial capital Tirin Kot, 360 kms south of the capital Kabul.
Charchino lies 30 kilometers southwest of Tirin Kot.
"A group of Taliban who came down from the mountains attacked their position," he said.
They then disappeared into the mountains.
Troop reinforcements have been sent to Charchino from Tirin Kot to pursue the attackers, the governor said.
Official sources in Oruzgan told Aljazeera that US forces headed to the scene to back up the Afghan troops.
The Taliban and allied anti-government fighters have a strong presence in the south of Uruzgan province, the birthplace of their fugitive leader Mullah Umar, and in the neighbouring northern districts of Kandahar province.
About 300 people have been killed in the past two months in attacks blamed on resurgent Taliban fighters.
The Taliban leadership was ousted by a US-led military assault two years ago.