As many as 36 suspected Islamic State militants were killed in the strike on Thursday evening in the eastern province of Nangarhar, Afghan defence officials said, adding there were no civilian casualties.
Amaq, the news agency affiliated with Islamic State in the Middle East, carried a statement denying that the group had suffered casualties in the attack, citing an unidentified source who had been in contact.
The statements could not be independently verified, and on Friday Afghan and foreign troops in the vicinity were not allowing reporters or locals to approach the scene of the blast.
The strike came as US President Donald Trump prepares to dispatch his first high-level delegation to Kabul, amid uncertainty about his plans for the nearly 9000 American troops stationed in Afghanistan.
Nicknamed "the mother of all bombs," the weapon was dropped from an MC-130 aircraft in the Achin district of Nangarhar, bordering Pakistan.
On Friday, US Army General John Nicholson said he was in constant communication with officials in Washington, but the decision to use the 9800kg bomb was based on his assessment of military needs and not broader political considerations.
"This was the first time that we encountered an extensive obstacle to our progress," he said of a joint Afghan-US operation that has been targeting Islamic State since March.
"It was the right time to use it tactically against the right target on the battlefield."
Afghan and US forces were at the scene of the strike and reported that the "weapon achieved its intended purpose,", Nicholson said.
Afghan Defence Ministry spokesman Dawlat Waziri said no civilians were harmed in the massive blast that targeted a network of caves and tunnels that had been heavily mined.
"No civilian has been hurt and only the base, which Daesh used to launch attacks in other parts of the province, was destroyed," Waziri said in a statement.
He was using an Arabic term that refers to Islamic State, which has established a small stronghold in eastern Afghanistan and launched deadly attacks on the capital, Kabul.
The GBU-43 is a GPS-guided munition that had never before been used in combat since its first test in 2003, when it produced a mushroom cloud visible from 32km away.
The bomb's destructive power, equivalent to 11 tonnes of TNT, pales in comparison with the relatively small atomic bombs dropped on Japan at the end of World War Two, which had blasts equivalent to between 15,000 and 20,000 tonnes of TNT.
MIXED REACTIONS
In Achin village, about 5km from the remote, mountainous area where the bomb was dropped, witnesses said the ground shook, but homes and shops appeared unaffected.
Qari Mehrajuddin first saw "lightning like a thunder storm" followed by the roar of an explosion, an all-to-familiar sound for residents of the war-torn area.
"I thought there was a bombing just outside my home," he said. In reality, the blast was around three miles away, its massive impact bigger than any before seen in the region.
Some locals welcomed the strike.
"If you want to destroy and eliminate Daesh, then even if you destroy my home we won't complain, because they are not human beings, they are savages," said Mir Alam Shinwari, using an Arabic term for Islamic State.
Away from Achin, reactions were mixed.
"The fact is that America used their big bomb here to test its effectiveness," said Kabul resident Asadullah Khaksar. "If America wants to eliminate Daesh, it is very easy because they created this group."
Residents of Achin said they had got used to seeing militants climbing up and down the mountain, making occasional visits to the village.
"They were Arabs, Pakistanis, Chinese and local insurgents coming to buy from shops in the bazaar," said Raz Mohammad.
Afghan President Ashraf Ghani's office said in a statement the attack was a part of a joint operation by Afghan and international troops.
"Afghan and foreign troops closely coordinated this operation and were extra cautious to avoid any civilian casualties," it said.
But former president Hamid Karzai condemned the use of the weapon on Afghan soil.
The Taliban, the main security threat to Afghan and NATO forces trying to quell their stubborn insurgency, also denounced the bombing.
"Using this massive bomb cannot be justified and will leave a material and psychological impact on our people," the Taliban, who compete with Islamic State in Afghanistan, said in a statement.
American officials said the bomb had been positioned for possible use in Afghanistan for "some time" since the administration of former president Barack Obama.
The United States has steadily intensified its air campaign against Islamic State and Taliban militants in Afghanistan, with the Air Force deploying nearly 500 weapons in the first three months of 2017, up from 300 in the corresponding 2016 period.
