At least eight Afghan troops were killed when a Nato air strike hit two military checkpoints in a volatile province near the capital, Kabul, on Monday.
An Afghan official described the friendly fire incident as an accident due to bad co-ordination.
The early morning strike took place in the Baraki Barak district of Logar province, about 50km from Kabul, according to Afghan provincial army commander Abdul Razaq.
Five other troops were injured, Mr Razaq added.
Logar police chief Mohammad Douod Ahmadi confirmed the casualty figures, though other Afghan officials gave slightly different numbers.
District governor Mohammad Rahim Amin said the Nato air strike was “likely a mistake, due to bad co-ordination” in an area where Taliban insurgents are highly active.
A US military spokesman in Afghanistan, Colonel Brian Tribus, said the coalition is aware of an incident in Logar.
“This incident is under investigation,” he said.
Security in Logar has deteriorated in recent months as the Taliban stepped up their attacks on Afghan soldiers and security forces, trying to spread their footprint across the country and take control of some remote regions.
The US and Nato forces concluded their combat mission at the end of last year and Afghan troops have since taken control of the country’s security, which has caused an increase in Afghan casualties.
AP