US forces said there were no civilian casualties in the attack in Garmsir.
Earlier on Friday the alliance had reported that six civilians were killed during a Nato-led operation against the Taliban in south of Afghanistan.
They died in Girishk district of Helmand on Wednesday when British-led forces under Nato's command launched a major operation in the district.
"We believe that six non-combatants were killed," Major Charles Anthony, a Nato spokesman, said.
Afghanistan has seen a steady escalation of violence over the last two years since Afghan and US-led forces toppled the Taliban in 2001.
About 168 international soldiers have been killed in Afghanistan this year.
Nicolas Sarkozy, the French president, expressed his condolences to all the victims of the Kabul attack, adding in a statement that he was "more determined than ever to continue the fight against terrorism."
On Thursday, one Nato soldier was killed in an ambush in neighbouring Uruzgan province where a day earlier more than three dozen fighetrs died in a 14-hour long battle with US-led and Afghan forces, Western military officials said.
Taliban leaders have denied suffering any losses in Uruzgan and said those killed were civilians. There was no immediate independent verification for either side's account.
More than 350 Afghan civilians have been killed during operations by Western forces this year, according to estimates by Afghan officials and aid agencies.
The casualties sparked protests demanding the resignation of Hamid Karzai, Afghanistan's president, and the withdrawal of US troops from Afghanistan.
Karzai, also facing criticism for perceived lack of development, corruption, growing insecurity and booming drugs, has repeatedly urged foreign troops to avoid civilian casualties while conducting operations.