Twenty people were killed in an ambush on a UN convoy transferring injured civilians to the country's central hospital.

civilians 是名词 civilian 的复数形式，civilian 指"平民、老百姓"，特指不属于军队、警察等武装力量的普通民众。这个词来自拉丁语 civilis（公民的），与军事人员形成对比。