BBC News with Sue Montgomery President Obama has confirmed the death of an American aid worker who was held hostage by Islamic State militants in Syria for 18 months. He said the killers of Kayla Mueller would be brought to justice. Gary O\'Donoghue reports from Washington. Islamic State had already said that Kayla Mueller was killed in an Jordanian air strike last Friday, but the White House spokesman Josh Earnest said it was not possible to be specific about how and when she died. __________________________________________________________________ What\'s become clear is that over the weekend Kayla Mueller\'s family received information from IS, which the intelligence services here analysed and which allowed them to conclude that she was dead. BBC新闻,苏?蒙哥马利报道. 奥巴马总统证实被叙利亚伊斯兰国武装分子挟持18个月的美国援助人员死亡.他表示凯拉?穆勒的凶手将被绳之以法.加里?奥多诺休华盛顿报道. 伊斯兰国表示凯拉?穆勒是在上周五的约旦空袭中丧生,但白宫发言人乔希?厄内斯特称不可能知道其具体的死因及死亡时间. ________________________________________________________________ 目前清楚的是,凯拉?穆勒家人周末收到了伊斯兰国的信息,据此情报部门分析并断定穆勒死亡.