IS chief strategist Abu Muhammad al-Adnani killed in Aleppo - Media
The Amaq news agency said Abu Muhammad al-Adnani died in Aleppo province, BBC reported.
The Pentagon said an air strike had targeted Adnani in the town of al Bab and the results were being assessed.
Reports of his death come as IS is suffering a series of military reverses in both Syria and Iraq.
Adnani - who was also the group's spokesman - was "martyred while surveying the operations to repel the military campaigns against Aleppo", Amaq said, without giving details about how he died.
In a statement, Pentagon spokesman Peter Cook described Adnani as the "principal architect of Isil's external operations."