At least 14 members of an Afghan family, including women and children, were killed when their minivan struck a roadside bomb in the country's restive south on Saturday, officials said.
The attack in the Marja district of Helmand province was the first major attack since the start of the holy Muslim fasting month of Ramadan.
"Fourteen civilians were killed and five others wounded in an IED (improvised explosive device) blast in Marja district of Helmand province. All of them were from the same family," deputy provincial governor Mohammad Jan Rasolyar told AFP.
Helmand police chief Nabi Jan Mullah Khel claimed a higher toll, saying 16 civilians, including women and children, were killed while three other civilians were wounded.
Haje Fateh Mohammad, a tribal elder from the region, said he counted 15 bodies as he helped retrieve them from the twisted carcass of the vehicle.
No group immediately claimed responsibility for the incident but the attack comes as the Taliban intensify their countrywide summer offensive despite repeated government attempts to reopen peace negotiations.
The insurgents launched a countrywide offensive in late April, stepping up attacks on government and foreign targets in what is expected to be the bloodiest fighting season in a decade.
The surge in attacks has also taken a heavy toll on civilians, according to the UN mission in Afghanistan.
Almost 1,000 civilians were killed during the first four months of this year, a sharp jump from the same period last year, it said.
Afghan authorities have repeatedly tried to jumpstart talks with the Taliban in the hope of ending the 13-year conflict, but the militants have set tough conditions, including the withdrawal of all foreign troops in Afghanistan.
Marja district in the Taliban hotbed of Helmand was the focus of a major US-led military offensive designed to clear out the insurgent group in early 2010.