'Complete lie'Witnesses say the suicide bomber had acted alone, that there were no accomplices and that US troops had panicked, firing at anything that moved immediately after the attack.
"We don't train or order our troops to fire on unarmed civilians, and it's uncertain at this time what caused the casualties"
Lieutenant Colonel David Accetta, coalition forces spokesman
One told Al Jazeera: "There were no gunmen, this is a complete lie. This is a peaceful area, we don't have guns."
The dead included an 80-year-old man, whose grandson said: "A bomb exploded, my grandfather sat in a car and at that time American soldiers were shooting into my grandfather's car."
Hamid Karzai, the Afghan president, condemned the killings earlier on Monday and ordered an investigation into Sunday's attack.
His office and the Afghan interior ministry on Monday put the death toll at 10 civilians while the coalition late on Sunday said eight Afghans were killed and 35 wounded.
Response
"We regret the loss of life of the Afghan civilians, but coalition forces were attacked by both a suicide bomb vehicle and small arms fire. "Our forces returned fire in self-defence against numerous enemy positions," said Lieutenant Colonel David Accetta, coalition forces spokesman.
"We don't train or order our troops to fire on unarmed civilians, and it's uncertain at this time what caused the casualties. "But it's important to note that the extremists conducted this attack in an area that they knew would cause civilian casualties," he said.
Civilian deaths
"Nato has done what they wanted to do. Now they should just leave Afghanistan and let people live their lives without anybody's help"
hiba, Jordan
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The Nato base in Kapisa is staffed by US forces. William Mitchell, a spokesman for the US military, said officials were looking into the incident.