Three Afghan civilians were shot dead and three others wounded when a French soldier opened fire on their vehicle in Kapisa province, north of the capital, French military and the Afghan presidency said.
The incident happened late Tuesday night when the driver of the car failed to stop after approaching soldiers on patrol, said the French military's spokesman in Kabul, Lieutenant Colonel Eric de Lapresle.
The dead were one pregnant woman, a young man and a child, according to a statement from the presidential palace, and the French military said one woman and two men were wounded.
Afghan President Hamid Karzai "strongly condemned" the attack that took place in the Alasau district of the eastern province.
"The incident happened as Nato forces opened fire on a car that was moving towards them, thinking it was a suicide car," said his statement.
"They opened fire on this car martyring one pregnant woman, one young man and a child..."
It said that the French ambassador in Kabul had called the presidential palace to officially apologise.