According to local government officials, many of the casualties in the Friday night raid on a village in Charcheno district were women and children.
A local police officer, who did not want to named, said six people had died and seven injured.
US military spokesman Lieutenant-Colonel Bryan Hilferty said he was unaware of any civilian casualties.
He said US planes had pounded suspected Taliban positions in the area on Friday morning in retaliation for the killing of two US soldiers on Thursday, and not on Friday night.
"I have no knowledge of this," he told Reuters news agency. "We dropped some bombs on Taliban positions yesterday morning not last night."
Hilferty said on Friday the air strikes against suspected Taliban positions were launched after two US soldiers and at least five fighters were killed in a clash the previous day.
He said US and Afghan National Army soldiers came under fire on Thursday while on patrol in a village in Uruzgan's Tarin Kot district.
The US has intensified its search
for Taliban and al-Qaida members
The incidents came amid a stepped up hunt by US-led forces for Taliban and al-Qaida fighters, including Usama bin Ladin, in southern and eastern Afghanistan launched on 7 March and codenamed "Mountain Storm".
The United States has been criticised by many Afghans and rights groups for inflicting civilian casualties in its war in pursuit of Taliban, al Qaida and allied fighters launched after the 11 September 2001, attacks on New York and Washington.
The United Nations has called for details of investigations into such incidents to be made public.
In further violence overnight, three fighters were killed when several dozen suspected Taliban and al-Qaida fighters attacked government forces near the US military base at Shkin in Paktika province close to the Pakistani border.
Paktika police chief Muhammad Rahim Ali Khel said the attackers struck from four directions firing heavy weapons. He said they fled into Pakistan when US helicopters appeared.
"Three of the Taliban and al-Qaida people were killed and there were no casualties on our side at all," he said.
"In a way I can say that we repelled the attack." It occurred just across the border from a major Pakistani military operation against hundreds of suspected al-Qaida fighters in Pakistan's South Waziristan region.
Uruzgan provinces had seen incidents in the past in which US bombing has killed civilians.
In the worst, in July 2002, 48 people were killed and 117 hurt when a US gunship attacked a wedding party in the province, according to figures from Afghan officials.
The US military eventually said 34 died and 50 were wounded - most women and children - but said the aircraft had come under fire.