Foreign troops killed nine Afghan soldiers in a mistaken air strike in the southeast of the country overnight, the Afghan Defence Ministry said.
Helicopter gunships pounded an Afghan army post on a road in Dowa Manda district of Khost province, a Taliban stronghold, district chief Lutfullah Babakarkheil said. Eight soldiers were killed and four wounded, he said.
The Afghan Defence Ministry in Kabul put the number of troops killed at nine.
The US military said Afghan soldiers may have been killed and wounded in a case of mistaken identity but said it did not have any casualty figures. It added that a coalition forces convoy was returning from an operation and was involved in "multiple engagements" that saw Afghan troops killed.
Nato's International Security Assistance Force (ISAF) said it was looking into the report. The vast majority of foreign troops in Khost are American.
Scores of Afghan civilians have been killed in air strikes by international troops in Afghanistan this year, Afghan officials say, feeding a perception that Nato-led and US coalition forces do not take enough care when calling in air support.
But it is still rare for foreign troops to hit their allies in the Afghan security forces.
Elsewhere, it was reported that 35 Taliban fighters were killed during a two-day battle in southern Uruzgan province that was led by Afghan forces and involved helicopter gunships.
Officials recovered the bodies of 35 Taliban fighters. Three police also died in the fight. Some 100 Taliban fighters were involved in the battle.
Violence in Afghanistan has reached its worst level this year since US-led and Afghan forces toppled the Taliban government in late 2001 for refusing to surrender al-Qaeda leaders behind the September 11th attacks on the United States.
Agencies