At least 11 civilians were killed in a roadside bombing in Afghanistan's Helmand province, authorities said on Saturday."A minibus carrying civilians hit an IED in Nawa district on Friday night.The blast completely destroyed the bus and killed all the people aboard," Xinhua news agency quoted an official as saying.The Taliban militant group uses improvised explosive devises to target security forces but the weapons also inflict casualties on civilians.The IED explosions are the third largest cause of civilian casualties in Afghanistan, following ground engagements and suicide attacks.Helmand, notorious for poppy growing, is a Taliban stronghold.