WASHINGTON (AP) — A senior Islamic State leader has been killed a U.S. raid in Syria, marking a further erosion of top leadership in the militant group in Syria and Iraq, U.S. officials said Friday.

The officials were not authorized to discuss the operation and so spoke on condition of anonymity.

It was not clear whether the operation involved members of the U.S. military's special operations task force that has been based in Iraq since early this year.

The identity of the senior leader who was killed in the latest U.S. raid also was not immediately available, as Defense Secretary Ash Carter and Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff, prepared to hold a Pentagon news conference Friday.

The U.S. military has killed numerous Islamic State leaders in recent months. Earlier this month the Pentagon said it killed Omar al-Shishani, described as the Islamic State's "minister of war," in an airstrike in Syria. In November, the Pentagon said an airstrike in Libya killed Abu Nabil, another top IS leader.