Islamic State has said that its spokesman and senior commander has been killed while overseeing military operations in northern Syria.
The IS-run Aamaq news agency said Abu Muhammed al-Adnani was "martyred while surveying the operations to repel the military campaigns in Aleppo".
His death, if confirmed, would be the latest blow to the group, which has been on the retreat in Syria and Iraq, where it has declared a self-styled Islamic caliphate straddling both countries.
Adnani, a senior leader in the group, has been the voice of IS over the past few years, and has released numerous, lengthy audio files online in which he delivered fiery sermons urging followers to carry out attacks.
Earlier this year, he called for massive attacks during the Muslim holy month of Ramadan.
He has also called for attacks in Western countries, telling Muslims in France on occasion to attack "the filthy French" in any way they could, including "crush them with your car".
He has also disparaged Saudi Arabia and its influential clerics for failing to rally behind the rebels that the monarchy supports in Syria like they did decades ago in Afghanistan.
— Samira Ghaderi (@Samira_Ghaderi) August 30, 2016
Aamaq vowed to gain revenge for the killing.
IS has suffered a string of defeats in recent weeks, including in Syria's northern Aleppo province, where Turkish troops and allied Syrian rebels drove the group out of the border town of Jarablus last week.
In Iraq, the group has lost its strongholds in Fallujah and Ramadi, in the western Anbar province. It still controls Mosul, but Iraqi forces are gearing up for a long-awaited operation to retake the country's second largest city.