The DAESH leader in Afghanistan and Pakistan, Hafiz Saeed Khan, was killed last month in an airstrike in Nangarhar province, the Pentagon confirmed on Friday.
Pentagon deputy press secretary Gordon Trowbridge said the strike came while US and Afghan special operations forces carried out counter-DAESH operations in southern Nangarhar province throughout July.
"During this time, US forces conducted an airstrike targeting Hafiz Saeed Khan, the Islamic State [also referred to as Daesh] in the Levant-Khorasan emir, in Achin district, Nangarhar province July 26, resulting in his death," Trowbridge said.
Saeed "was known to directly participate in attacks against US and coalition forces, and the actions of his network terrorized Afghans, especially in Nangarhar," he added.
Details of the strike were not immediately available, but a US official told the BBC that Saeed was killed by drone.
The death of Hafiz Saeed Khan is a blow to efforts by DAESH, to expand from its heartlands in Syria and Iraq into Afghanistan and Pakistan.
It is the second US killing of a prominent militant in the region in months. In May, a U.S. drone killed Afghan Taliban leader Mullah Akhtar Mansour in a strike in Pakistan.
A US government report said Afghan forces has lost 5 percent of territory this year. Despite that, Afghanistan's 15-year-old war grinds on with no clear victory in sight. Taliban fighters have been threatening at least two provincial capitals this summer, in Helmand and Kunduz.
In terms of its own territory, DAESH has been largely confined to a handful of districts in Afghanistan's Nangarhar province, which borders Pakistan, where DAESH militants, mostly defectors from the Taliban, are blamed for raiding villages and government outposts.
Both the Pakistani Taliban and DEASH have claimed responsibility for a horrific suicide bombing on Monday at a hospital in Pakistan which killed 73 people.
The DEASH group has also claimed responsibility for a July 23 attack in Kabul that killed dozens of people and left hundreds maimed.
Afghan forces, backed by the American military, killed an estimated 300 Daesh fighters in an operation mounted two weeks ago, the top US and NATO commander in Afghanistan said on Wednesday, calling it a severe blow to the group.
Khan has been reported dead before. But a claim by Afghan intelligence agents last year that he had been killed was never confirmed.