The dreaded outfit vowed to avenge the death of one of its most prominent and longest-serving leaders, according to media reports.
The Pentagon said it had targeted Adnani in a precision strike near the town of Al Bab in Aleppo province and was still assessing the results.
"Today, coalition forces conducted a precision strike near Al Bab, Syria, targeting Abu Muhammad Al-Adnani, one of ISIL's most senior leaders," Pentagon Press Secretary Peter Cook said.
The terror group had announced Adnani's death through its news outlet, Amaq, yesterday, saying he was "martyred while surveying the operations to repel the military campaigns against Aleppo".
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Adnani had served as principal architect of the terror group's external operations and as its chief spokesman.
Adnani had coordinated the movement of ISIS fighters, directly encouraged lone-wolf attacks on civilians and members of the military and actively recruited new members, the Pentagon spokesperson said.
"The US military will continue to prioritise and relentlessly target ISIL leaders and external plotters in order to defend our homeland, our allies and our partners, while we continue to gather momentum in destroying ISIL's parent tumour in Iraq and Syria and combat its metastases around the world," Cook said.