The Afghan government has launched an investigation into reports that up to 33 civilians were killed in a US and Afghan army operation.
The deputy governor of the eastern province of Nuristan told the BBC they died in heavy fighting at the weekend.
The US military said several insurgents were killed but that it had no reports of civilian deaths.
Afghan President Hamid Karzai has repeatedly urged the US and Nato to take care to avoid civilian casualties.
Nuristan is a remote and mountainous region and reports of the operation and casualties are difficult to verify.
The US-led coalition said the area had been identified as a stronghold of support for fighters loyal to the warlord Gulbuddin Hekmatyar.
Gulbuddin Hekmatyar has long been a thorn in the coalition's side
The coalition said its forces, along with the Afghan army, detained numerous insurgents, secured several compounds and captured weapons in the operation.
The Afghan defence ministry said it had no information on civilian deaths in Nuristan but had asked the army to investigate.
It said militants had suffered "heavy casualties".
The provincial deputy governor, Mohammad Aleem, said women and children were among those killed in the operation in Dohabi district.
The BBC's Alix Kroeger in Kabul says the issue of civilian casualties is one of the most difficult for international and Afghan forces.
They know it risks undermining support for them among Afghan communities and gives valuable propaganda material to their enemies, she says.