A bomb ripped through a vehicle northeast of Kabul on Tuesday and killed six Afghan civilians, including two children, the interior ministry said.
It was not immediately clear if the bomb was planted in the road, which runs past the largest US military base in Afghanistan, or was fixed to the vehicle, interior ministry spokesman Zemarai Bashary told AFP.
"Two men, two women and two children are killed," he said.
There was no immediate claim of responsibility for attack. Such blasts are usually directed at the Afghan or foreign security forces that are trying to put down an insurgency led by the Taliban.
It comes a week after another bombing in the same area killed three US troops serving with a NATO-led International Security Assistance Force (ISAF) as well as three Afghan civilians.
Insurgents have stepped up bomb attacks in Afghanistan in recent weeks after vowing in April to widen their campaign against the government.