WASHINGTON (AP) — The Pentagon says that U.S. forces killed the head of the Islamic State group affiliate in Afghanistan in an airstrike in Kunar province earlier this week.

Defense Secretary Jim Mattis says that killing Abu Sayed is significant because the loss of leadership sets insurgent groups back for days or weeks.

IS in Afghanistan is known as the Islamic State-Khorasan group. The U.S. and Afghan forces launched an offensive against the IS group in early March, as the militants were gaining a foothold in eastern Afghanistan.

Mattis tells Pentagon reporters that taking out a leader creates disarray in the ranks. He declines to provide any additional details on the strike.

A chief Pentagon spokesperson, Dana White, says that Abu Sayed was killed on Tuesday along with other members of the group.