The Islamic State group says its spokesperson has been "martyred" in northern Syria, the AP reports. The IS-run Aamaq news agency said Tuesday that Abu Muhammed al-Adnani was "martyred while surveying the operations to repel the military campaigns against Aleppo," without providing further details. IS has released several audio files online in which Adnani, a senior leader in the group, delivers fiery sermons urging followers to carry out attacks. The extremist group has suffered a string of defeats in recent weeks, including in Syria's northern Aleppo province, where Turkish troops and allied Syrian rebels drove IS out of the border town of Jarablus last week. (More ISIS stories.)