Afghan officials say a roadside bomb has killed at least seven members of a family travelling in a trailer towed by a tractor in southern Afghanistan.

The Interior Ministry said in a statement that the vehicle hit the bomb on a road in the Mali Zai region of Zabul province just after daybreak on Monday. It said four other people were wounded by the blast, which the ministry blamed on the Taliban.

A spokesman for the provincial governor, Shareef Nasari, says the death toll could be as high as eight. He says all the dead are members of the same family.

Violence has been increasing around Afghanistan in recent weeks as fighting escalates in the spring. The harsh Afghan winter often puts a damper on fighting.