Local villagers in Afghanistan have contradicted US reports that the target of an air strike that killed nine children also died in the raid.
The US sent in an A-10 "Warthog" after receiving intelligence
The attack was carried out on Saturday in the village of Hutala, in a remote area of southern Ghazni province.
US officials said they were acting on extensive intelligence and had killed a former Taleban militant, Mullah Wazir.
But local Afghans told the BBC's Crispin Thorold the intended target had left the village 10 days earlier.
President Hamid Karzai has expressed his shock at the incident.
He said his government had sent a team of investigators to the scene and had also sent officials to ensure the victims' families were being helped.
The Afghan president said US forces should ensure that future operations were better co-ordinated with the Afghan Government to ensure such incidents would not happen again.
The United Nations has also condemned the incident as "profoundly distressing " and called for a swift inquiry.
Patches of dried blood and a pitiful pile of children's hats and shoes are the only evidence that remains of a bombing raid that went dreadfully wrong, our correspondent says.
Seven boys, two girls and a 25-year-old man were killed when two A-10 American planes fired rockets and bullets into a group of villagers sitting under the shade of a tree at about 1030 local time (0600 GMT) on Saturday, he says.
Only one house was hit in the attack - but accounts differ on whether it belonged to the militant targeted.
US ground forces found the bodies of the children near that of the intended target after the strike, US military spokesman Major Christopher West said.
A commission has been formed to investigate the incident, he said, adding that the US military regretted the loss of innocent life.
The targeted militant, Mullah Wazir, a former low-ranking member of the Taleban, was thought to be behind the murders of two foreign contractors working on a ring road.
But local villagers said the young man who died was a civilian.
Mullah Wazir's house was not damaged in Saturday's raid, they told our correspondent.
Dec 2001: 65 killed in bombing of convoy of tribal elders
April 2002: Four Canadian soldiers killed
July 2002: 48 killed when bomb hits wedding party
April 2003: 11 killed by bomb in village of Shkin
Dec 2003: Nine children killed by bomb near Ghazni
*Mistakes accepted by US
There was further confusion on this point: Reuters news agency quoted Haji Assadullah, governor of Ghazni province, as saying: "It has not been ascertained if Mullah Wazir was killed or not, but the house was his."
There is strong support in the area for the ousted hardline Islamic Taleban and the Hezb-e-Islami group, also fighting the coalition.
Five more people working on reconstruction projects have been kidnapped in the past three days - two Indians, and two Turks and an Afghan working with them.
The kidnappers are not reported to have had any contact with the authorities.
Saturday's bombing is the latest in a series of attacks by US-led forces which have resulted in the deaths of dozens of Afghan civilians since the start of the campaign against the Taleban and al-Qaeda in October 2001.
Although in many areas Afghans welcome the presence of American troops and other foreigners, there is hostility in some southern and eastern parts, our correspondent says.