US-led coalition and Afghan troops have raided houses in the east of the country, killing at least four people.
Villagers said the four men who died in Nangarhar province, 50km (30 miles) west of Jalalabad, were civilians who had nothing to do with militancy.
But the coalition said it had raided compounds suspected to be "harbouring Taleban and foreign fighters".
Violence has soared in recent months, and foreign forces have frequently been accused of causing civilian deaths.
Friday morning's incident happened in the village of Nokrukhel in Sherzad district of Nangarhar province.
President Karzai has accused foreign troops of being reckless
Coalition forces said credible intelligence had led them to three separate compounds suspected of harbouring Taleban and foreign fighters who had previously targeted Afghan and coalition forces.
"Taleban forces inside two compounds attempted to engage coalition forces as they approached," a coalition statement said.
It said coalition troops had shot the militants dead and found weapons in the houses. Sixteen "militants" were also detained during the operation, the statement added.
But a local villager Ketab Jan told the BBC that the forces had killed "four innocent people from one family - the father, two sons and a grandson".
Mr Jan said the soldiers had recovered opium and not weapons from the four men.
Human rights activist Lal Gul, who is from the same area, also said the four men were "innocent civilians".
He told Reuters news agency that an 85-year-old man, Mohammada Jan, two of his sons and a grandson had been killed by troops who first "blew up the gate of [the man's] house".
"From there they went to several other houses, broke into them and arrested 15 civilians," he said.
A local police spokesman, Col Ghafoor Khan, partially supported the American account by saying weapons were found in the houses. He said the four people killed were regarded as suspects by the Afghan police.
Ten days ago, there was a similar incident in the south when the coalition raided a house and killed a man, saying he was a militant. But the family and local people insisted he was innocent.
Last week, President Hamid Karzai blamed foreign troops for ignoring Afghan advice and said "innocent people were becoming victims of [their] reckless operations".
He was speaking after a week in which up to 90 Afghan civilians were killed.
More civilians have been killed this year as a result of foreign military action than have been killed by insurgents in suicide bombings and other attacks, correspondents say.
Separately, one Afghan was killed and six others wounded during a suicide bomb attack near a convoy carrying foreign troops in Paktika province, a statement issued by the combined forces said.
The injured included two foreign soldiers.
Initial reports suggest that a transport truck, carrying wood, drove into the convoy and exploded.