US drops 'Mother Of All Bombs' on ISIS caves in Afghanistan

WASHINGTON (KABC) -- The United States dropped the military's largest non-nuclear bomb on an Islamic State target in Afghanistan on Thursday, the Pentagon announced.

It was the first combat use of the bomb, known as the GBU-43, which the Pentagon said contains 11 tons of explosives and weighs 22,000 pounds.

"At about 7 p.m. local time in Afghanistan last night the United States military used a GBU-43 weapon," White House Press Secretary Sean Spicer said at a press conference Thursday morning. "The GBU-43 is a large and powerful and accurate weapon."

The Air Force calls it the Massive Ordnance Air Blast bomb. Based on the acronym, it has been nicknamed the "Mother Of All Bombs" since it was first developed in 2003. It is designed to hit softer targets such as surface facilities, tunnel entrances and troop concentrations.

The bomb is so large that it is carried in the cargo hold of the aircraft then rolled out the plane's rear door toward its target.

"We targeted a system of tunnels and caves that ISIS fighters used to move around freely making it easier for them to target U.S. military advisers and Afghan forces in the area," Spicer said. "The United States takes the fight against ISIS very seriously and in order to defeat the group we must deny them operational space, which we did."

The Pentagon said the cave complex was located in the Achin district of Nangarhar province, very close to the border with Pakistan. The U.S. estimates 600 to 800 IS fighters are present in Afghanistan, mostly in Nangarhar.

"As ISIS-K's losses have mounted, they are using IEDs, bunkers and tunnels to thicken their defense," said Gen. John W. Nicholson, commander, U.S. Forces - Afghanistan, in a written statement. "This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K."

The Pentagon and Spicer said the U.S. took all precautions necessary to prevent civilian causalities and collateral damage. The Pentagon said it had no early estimate of deaths or damage caused by the operation, which President Donald Trump called a "very, very successful mission."

Afghan forces and the American troops advising them have engaged in heavy fighting with ISIS forces in Afghanistan over the past year.

An American special operations soldier was killed this past weekend in combat operations against ISIS in Nangarhar Province.

ABC News and the Associated Press contributed to this report.