At least four students were killed and 17 others, including two teachers, sustained injuries as a mortar mine struck a school in Afghanistan's Ghazni province on Saturday, officials said.According to provincial government spokesman Aref Nuri, the mortar mine struck Mullah Noh Baba school in Andar district, Xinhua news agency reported. It hit the school when fierce fighting was going on between government forces and the Taliban militants, according to villagers, saying no one knew which side fired the mortar.Civilians mostly bear the brunt of war in the war-battered Afghanistan as 3,804 civilians, including 927 children were killed and over 7,100 others injured in 2018, according to a report of the UN Assistance Mission in Afghanistan released here last month.