The attack infuriated villagers who took the bodies to Kandahar city
Three children and a man have been killed in an overnight air strike by international forces, angry villagers in southern Afghanistan say.
The bodies were taken to the city of Kandahar to be displayed in front of officials. US and Nato-led forces said they were investigating the reports.
The issue of civilian casualties at the hands of foreign troops has caused deep resentment among Afghan people.
President Hamid Karzai has repeatedly spoken out against such incidents.
Gen Stanley McChrystal ordered troops to limit the use of airstrikes to prevent civilian casualties soon after assuming command of Nato and US forces last month.
The US military said it had killed four insurgents on motorcycles in the area of the alleged airstrikes, but could not confirm any civilian fatalities.
Concern about civilian deaths has prompted a shift in the US approach
A reporter for the Associated Press news agency witnessed residents of Kowuk bring the bodies of three boys and a man to the guesthouse of the Kandahar governor from their village, 20km (12 miles) north of the provincial capital, Kandahar city.
The villagers shouted "Death to America! Death to infidels!" as they displayed the corpses in the back of a pickup truck.
The father of the dead boys, Abdur Rahim, told AP that he heard a pair of helicopters circling over his compound early on Wednesday before they fired two missiles that hit his home.
His brother and another son were wounded, he said.
"What was the fault of my innocent children? They were not Taliban," Mr Rahim said.
"Did they come here to build our country or kill our innocent children?"
A US military spokeswoman confirmed that a helicopter had fired on four insurgents who were carrying jugs on motorcycles through a field away from a populated area of the local district, Arghandab.
"The helicopter engaged the militants with guns and rockets, however the explosions heard by locals were caused by the jugs exploding," Capt Elizabeth Mathias told AP.
She said that commanders on the ground were checking into reports of the civilian deaths.
Last week the UN said the number of civilian casualties in Afghanistan had increased by nearly 25% in the first half of 2009 compared to the same period last year.
Separately, officials in the eastern province of Nangarhar said two tribal elders and their four bodyguards were killed by a roadside bomb.
Insurgent groups regularly carry out such attacks.
The violence came as the new secretary-general of Nato, Anders Fogh Rasmussen, is in Afghanistan for talks on security ahead of this month's presidential and provincial elections.
Mr Rasmussen will be meeting the Afghan leadership, presidential candidates and senior officers from the Nato-led force which currently has more than 60,000 troops in the country.