At least three civilians were killed and another injured when a blast rocked northern Afghanistan's Takhar province on Friday, police said.The blast took place inside a house in Chahab district, Xinhua news agency quoted a senior police official as saying.With civilians often bearing the brunt of war in conflict-hit Afghanistan, the United Nations Assistance Mission in Afghanistan (Unama) documented 2,181 civilian casualties (715 dead and 1,466 injured) in the first quarter of 2017, a report said.