In a statement distributed by the group's supporters, Amaq News Agency reported that Abu Muhammad al-Adnani died in the province of Aleppo.
He was "martyred while surveying the operations to repel the military campaigns against Aleppo", it said.
Adnani was known for his calls for lone-wolf attacksin the West.
One of the group's founder members, he is also said to have masterminded attacks in Europe and elsewhere.
