The United States has dropped the largest non-nuclear bomb it has ever used in combat, The Telegraph said.

The 21,000 pound device was dropped on an Islamic State cave tunnel complex in a remote area of eastern Afghanistan.

It's official name is the Massive Ordinance Air Blast (MOAB) bomb but it is widely known in the U.S. military as the "Mother Of All Bombs".

It was the first time the bomb has been used against an enemy.

The bomb, also known as the GBU-43B, was dropped in the Achin district of Nangarhar province, close to the border with Pakistan.

Because of the size of the 30ft-long bomb a cargo plane with a rear door, a U.S. Air Force MC-130, had to be used and it was pushed out of the aircraft rather than dropped from a bomb bay.

A damage assessment was being carried out.

While the MOAB was 21,000 pounds each of the Tomahawks dropped in Syria was 1,000 pounds.

Sean Spicer, White House spokesman, said the bomb was dropped at 7pm local time in Afghanistan.

He said: "We targeted a system of tunnels and caves Isis fighters used to move around freely, making it easier for them to target U.S. advisers and Afghan forces. We must deny them operational space.

"The U.S. took all steps to avoid civilian casualties and collateral damage."