Fourteen Afghan civilians, including women and children, have died as their minibus hit a roadside bomb in southern Helmand province, Afghan officials say.
Four others were injured when the vehicle was hit by a Taliban-planted bomb, Dawood Ahmady, a spokesman for Helmand's governor, told the BBC.
It happened in a crowded area of Nahr-e Saraj district, said Nato.
The Taliban have used such bombs to kill hundreds of soldiers and police.
The BBC's Bilal Sarwary in Kabul says the device went off in an area not far from an Afghan National Army base.
'Ignorant and savage'
The device was planted on a busy intersection of the main road running from the city of Kandahar to the western Afghan province of Herat.
President Hamid Karzai sent his condolences to the victims' loved ones, and said: "Killing of innocent Afghans and laying bombs on highways is the work of ignorant and savage people."
The Taliban have not commented on whether they planted the bomb.
Nato's International Security Assistance Force said earlier that the blast had killed more than 10 people.
Violence is at its worst in Afghanistan since the US-led invasion of 2001, with civilians often bearing the brunt.
While more than 700 foreign troops are recorded killed this year in Afghanistan, the UN say over 2,400 civilians died in the conflict during the first 10 months of this year.