"It was a car that refused to stop at a checkpoint in spite of repeated warnings, and was in effect the target of a defensive shooting, as is the rule," Gerard Longuet said on a visit to Rome.
Three Afghan civilians -- a man, a woman and a child -- were shot dead and three wounded when a French soldier opened fire on their vehicle in Kapisa province, north of the capital on Tuesday night, the French military and the Afghan presidency said.
Expressing "deep sorrow for the victims", the minister underlined the incident happened in an area under military control that frequently saw attempted suicide attacks with cars trying to ram into soldiers.
"We are saddened by this misunderstanding that could have been avoided if the car had respected the security rules that apply to each Afghan citizen stopped at a roadblock," Longuet said.
The minister was in Rome for talks with his Italian counterpart Ignazio La Russa.
A suicide attack in the Tagab valley of Kapisa killed five French soldiers on July 13th.