At least six civilians were killed and three injured on Tuesday in a roadside bombing in Afghanistan's Ghazni province, an official said.The roadside bomb in Ghazni province's Deyak district claimed six lives including three children, Xinhua quoted spokesman for provincial government Shafiq Nang as saying.A total of 1,592 civilians have been killed and 3,329 others injured in the first six months of this year in the militancy plagued country, according to a report released by UN Assistance Mission in Afghanistan in August.