WASHINGTON—U.S. military officials on Sunday introduced Apache helicopters into the campaign against Islamic State militants in Iraq’s embattled Anbar province, marking the closest air support the U.S. has provided since it began airstrikes in early August.

The use of Apache AH-64 helicopters provided new capabilities in the U.S. fight against Islamic State, also known as ISIS or ISIL. The attack helicopters come equipped with a wider array of sensors and targeting devices than other aircraft used in the military operation....