DEVELOPING: The leader of the Islamic State (ISIS) terror group in Afghanistan and Pakistan was killed by a U.S. drone last month, a U.S. defense official confirmed to Fox News Friday.

The operation agaisnt Hafiz Saeed Khan was first disclosed by Afghanistan’s ambassador to Pakistan. 

Omar Zakhilwal told Reuters: “I can confirm that ISIS Khorasan leader Hafiz Saeed Khan, along with his senior commanders and fighters died in a U.S. drone strike on July 26 in Kot district of Afghanistan’s Nangharhar province.”

Khan, a former member of the Pakistani branch of the Taliban, had sworn allegiance to Middle East-based ISIS.

He was earlier reported killed last year but the death was never confirmed.

Khan’s death is a blow to efforts by ISIS to expand its territory and its jihadist push into Afghanistan and Pakistan.

It would be the second death of a prominent jihadist in the region in months. Afghan Taliban leader Mullah Akhtar Mansour was killed by a US airstrike strike in Pakistan in May.

Fox News’ Lucas Tomlinson contributed to this report.

Click for more from