The NATO force in Afghanistan said Sunday three civilians -- two children and a tribal leader -- were killed in incidents in which its troops opened fire, including after coming under attack by Taliban. The issue of civilian casualties from operations against insurgents is one of the most controversial aspects of the foreign military presence in Afghanistan, angering the public and government of President Hamid Karzai. The children were killed on Saturday, when troops from NATO's International Security Assistance Force fought Taliban militants who had attacked from a compound in Helmand province, a hotbed of the insurgency, ISAF said.