The 30-year-old better known as Omar the Chechen, reportedly died in combat near the Iraqi city of Shirqat, 100km from the ISIS stronghold of Mosul.
The Pentagon is verifying whether al-Shishani died in a US drone strike carried out earlier this month, officials told CNN. Washington previously boasted that it took out al-Shishani, who has a $5 million bounty on his head, in Syria in March, only to backtrack when Islamic State said he survived his injuries.
Al-Shishani was born into a mixed Georgian-Chechen family, and served in a spec ops unit in the Georgian army, before volunteering to join Islamic State three years ago. He was reportedly consulted by ISIS leader Abu Bakr al-Baghdadi on key military movements, as the Islamist group expanded its reach, earning the the title 'minister of war.'