“Twelve civilians, among them women and children, were killed today when their van hit in a roadside bomb,” said Daud Ahmadi.
He added that the civilians were travelling from provincial capital Lashkar Gah to Sangin district when the blast took place.
The deaths came the day after 59 people died in two blasts at Shia shrines, 55 of them in Kabul.
Roadside bombs are frequently planted by Taliban-led insurgents fighting a decade-long war against Nato-led foreign troops and Afghan government forces.
There are around 140,000 international troops, mainly from the United States, in Afghanistan helping government forces combat the insurgency.
According to the UN, the number of civilians killed in violence in Afghanistan rose by 15 per cent in the first six months of this year to 1,462, with insurgents blamed for 80 per cent of the killings.
