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PESHAWAR, Pakistan — The leader of ISIS in Afghanistan and Pakistan was killed in a U.S. drone strike in Afghanistan's Nangarhar province, Afghan officials told NBC News — although U.S. officials said they are doubting reports of his death.

Hafiz Saeed Khan is the head of an area called Khorasan, comprised of Pakistan, Afghanistan and India, according to Afghanistan's National Directorate of Security. He and other top commanders were killed during a gathering on Friday, the intelligence agency said.

Defense and military officials said the U.S. has no proof or confirmation that he has been killed.

Hafiz Saeed Khan, a top ISIS commander in Afghanistan, was killed by U.S. air strikes in the Nangarhar province, Afghan officials said Saturday. Afghanistan National Directorate

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According to those same officials, three U.S. drone strikes on July 5 and 7 against terrorist militant groups are believed to have killed “several dozen” suspected ISIS and Taliban militants.

"Were there some leaders among those killed? Probably, but we have no confirmation" — and no firm evidence that Khan is among the dead, said senior U.S. military official.

Related: Afghan Taliban Contends With ISIS Encroachment

But his death, if true, would be a huge loss to ISIS.

Khan, who is Pakistani, is one of a small number of former Taliban militants who switched their allegiance to the terror network. After developing differences with Maulana Fazlullah, the chief of the Pakistani Taliban, Khan and his close commanders left the mainstream militant group and joined ISIS in October 2014.

A senior ISIS commander, Mufti Hasan, told NBC News a few months ago that they had declared the mountainous Tirah valley in the Khyber region as ISIS' headquarters.

Related: Afghanistan Battling Militants From 10 Countries: Ashraf Ghani

Speaking under condition of anonymity, a senior member of the Afghan Taliban said Khan was known for his harsh policies and ruthlessness.

"In their clashes with the Afghan Taliban, he and his men had beheaded dozens of Taliban fighters. They did not even spare women in the fighting and ruthlessly beheaded them," the Taliban commander said.

If he has died, Khan is the fourth high-ranking member of the militant group to be killed by U.S. strikes in the region over the past week, Reuters reported.