Règle correspondante
Practice Relating to Rule 1. The Principle of Distinction between Civilians and Combatants
Section C. Attacks against civilians
Nigeria’s Military Manual (1994) and Soldiers’ Code of Conduct state: “Civilian persons and objects must be spared.” 
Nigeria, International Humanitarian Law (IHL), Directorate of Legal Services, Nigerian Army, 1994, p. 39, § 5(c); Code of Conduct for Combatants, “The Soldier’s Rules”, Nigerian Army, undated, § 3.
The Report on the Practice of Nigeria confirms the existence of a norm of a customary nature prohibiting direct attacks against civilians and cites Nigeria’s Operational Code of Conduct in this respect. The report also states that, according to Nigeria’s opinio juris, the prohibition of direct attacks against civilians is part of customary international law. 
Report on the Practice of Nigeria, 1997, Chapter 1.4.