By Barbara Starr and Ryan Browne CNN

WASHINGTON (CNN) -- The US military has dropped an enormous bomb in Afghanistan, according to four US military officials with direct knowledge of the mission.

A GBU-43/B Massive Ordnance Air Blast Bomb, nicknamed MOAB, was dropped at 7 p.m. local time Thursday, the sources said.

The MOAB is also known as the "mother of all bombs." A MOAB is a 21,600-pound, GPS-guided munition that is America's most powerful non-nuclear bomb.

The bomb was dropped by an MC-130 aircraft, operated by Air Force Special Operations Command, according to the military sources.

They said the target was ISIS tunnels and personnel in the Achin district of the Nangarhar province.

The military is currently assessing the damage. Gen. John Nicholson, commander of US forces in Afghanistan, signed off on the use of the bomb, according to the sources.

This is the first time a MOAB has been used in the battlefield, according to the US officials. This munition was developed during the Iraq War.

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