One of the longest-serving and most prominent leaders of so-called Islamic State (IS) has been killed in Syria, IS-affiliated media say.The Amaq News Agency reported that Abu Muhammad al-Adnani had died in the province of Aleppo.The Pentagon said it had targeted Adnani in a precision strike near the town of al Bab and was still assessing the results. Adnani was known for his calls for lone-wolf attacks in the West, reports BBC.He was ‘martyred while surveying the operations to repel the military campaigns against Aleppo’, Amaq said.Fighting has escalated in the city in recent weeks, with rebels breaking a siege by government forces and Syrian and Russian warplanes carrying out air strikes on rebel-held areas.In a statement, Pentagon spokesman Peter Cook described Adnani as the ‘principal architect of Isil’s external operations’, using an alternative name for the group.He had ‘co-ordinated the movement of Isil fighters, directly encouraged lone-wolf attacks on civilians and members of the military and actively recruited’ new members, Mr Cook said.He added: ‘We are still assessing the results of the strike, but al-Adnani’s removal from the battlefield would mark another significant blow to Isil.’