The Pentagon has confirmed that the United States has dropped the largest non-nuclear bomb it has in its arsenal on a target in eastern Afghanistan.
The GBU-43 bomb is known as a Massive Ordnance Air Blast (MOAB), or the "Mother of All Bombs".
It is the first time this bomb has been used in combat.
US President Donald Trump has described the dropping of the bomb as "another successful job".
Speaking in the White House as he met first responders from the state of Georgia, he said he was "very proud of my military".
Asked whether he had specifically authorised this bombing and the use of this bomb, Mr Trump replied "what I do is I authorise my military", that "everybody knows exactly what happened".
He said he did not know if it sent a message to North Korea and that it did not "make any difference if it does or not".
He said North Korea was "a problem" and that he thought China was "working very hard" to deal with it.
Mr Trump also said the bombing was evidence of a more muscular US foreign policy since he took office in January.
Earlier, the Pentagon said it was targeting a series of caves and bunkers believed to be used by the so-called Islamic State group in the Achin district in the Nangarhar province, close to the border with Pakistan.
It was not immediately clear how much damage the device did.
The strike occurred at about 7:32pm local time (4.02pm Irish time).
US drops largest non-nuclear bomb in arsenal on Afghan caves - @CaitrionaPerry reports. More: https://t.co/i1F6MO7p1z pic.twitter.com/sPBAY946IL
— RTÉ News (@rtenews) April 13, 2017
The GBU-43 is a 9,797kg, GPS-guided munition and was first tested in arch 2003, just days before the start of the Iraq war.
The security situation in Afghanistan remains precarious, with a number of militant groups trying to claim territory more than 15 years after the US invasion which toppled the Taliban government.
White House spokesman Sean Spicer opened his daily news briefing speaking about the use of the bomb and said, "We targeted a system of tunnels and caves that ISIS fighters used to move around freely, making it easier for them to target US military advisers and Afghan forces in the area."
Last week, a US soldier was killed in the same district as the bomb was dropped while conducting operations against IS.
"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," Mr Spicer said.
Mr Spicer was asked whether Mr Trump directly authorised this strike and what the timeline leading up to the decision was, but he chose not to answer and referred all queries to the US Department of Defence.
On US dropping 21600lb (9798kg) bomb in Afghanistan,@PressSec says it targeted ISIS tunnels &caves to "deny them operational space" @rtenews pic.twitter.com/rbyGd076PX
— Caitriona Perry (@CaitrionaPerry) April 13, 2017
A CNN military analyst, Lieutenant General Mark Hertling, expressed surprise that the bomb has been dropped, as this weapon has not been talked about for a long time.
As well as the explosion, it causes a massive concussive impact which delivers a serious psychological blow to those who are not killed by the blast.
The bomb sends shock waves which reverberate through the tunnel network which was targeted.
It destroys everything in the "circle of impact."
