"US forces killed Abu Sayed, the emir of Islamic State of Iraq and Syria -- Khorasan Province (ISIS-K) -- in a strike on the group's headquarters in Kunar Province, Afghanistan, July 11," Pentagon spokeswoman Dana White said in a statement on Friday.

"The raid also killed other ISIS-K members and will significantly disrupt the terror group's plans to expand its presence in Afghanistan."

Abu Sayed was chosen to lead the group after Afghan and US forces killed former Daesh-K leaders Abdul Hasib and Hafiz Sayed Khan in April this year and July last year respectively.

This comes a few hours after Pentagon chief Jim Mattis said that Daesh chief Abu Bakr al-Baghdadi, who has been reportedly killed in recent months in Syria, might still be alive.

"If we knew, we would tell you -- right now, I can't confirm or deny it," Mattis told reporters on Friday.

"Our approach is we assume he's alive until it's proven otherwise, and right now I can't prove it otherwise,” he added.