The Amaq news agency reportedly said Abu Muhammad Al-Adnani, who was the chief strategist of Islamic state group, died in Aleppo province, Syria.
It is said that an air strike had targeted Adnani in the town of al-Bab and the results were being assessed.
Adnani was also the group’s spokesperson. Amaq said, “He was martyred while surveying the operations to repel the military campaigns against Aleppo”.
Pentagon spokesman Peter Cook described Adnani as the “Principal Architect of Isil’s external operations”, using an alternative name for the group.
He said, “We are still assessing the results of the strike, but al-Adnani’s removal from the battlefield would mark another significant blow to Isil.’
Fighting has escalated around the city in recent weeks, with rebels breaking a siege by government forces and Syrian and Russian warplanes bombing rebel-held areas.