The leader of the Islamic State branch that operates in Afghanistan and Pakistan, Hafiz Saeed Khan, was killed in a US airstrike on 26 July in eastern Afghanistan, the Pentagon said on Friday.
It was the US military's second killing of an anti-American Islamist militant leader in the region in the past three months.
In a statement, Gordon Trowbridge, a deputy spokesman at the Defense Department, said the targeting of the Islamic State branch leader was part of an operation by US and Afghan forces in Nangarhar province, which borders Pakistan and is a hotbed of jihadi groups.
Khan, a former member of the Pakistani Taliban, had been the commander of the Islamic State in the Khorasan, an ancient name for the region that includes Afghanistan and Pakistan.
Trowbridge's statement said Khan had been known to ''directly participate in attacks against US and coalition forces, and the actions of his network terrorized Afghans, especially in Nangarhar''.
The statement said that Khan had used Nangarhar to ''train, equip, disseminate and control'' the supply of fighters, and that his death would disrupt the branch's recruiting and operations in the region.
In May, US officials said a US drone strike in Pakistan had killed the leader of the Taliban, Mullah Akhtar Muhammad Mansour.
That operation was considered the most significant US raid inside Pakistan since al-Qaeda's leader, Osama bin Laden, was killed in 2011.