The US military's largest non-nuclear bomb killed dozens of Islamic State militants as it smashed their mountain hideouts, Afghan officials said Friday, ruling out any civilian casualties despite the weapon's destructive power.
The GBU-43/B Massive Ordnance Air Blast bomb -- dubbed the "Mother Of All Bombs" -- was unleashed in combat for the first time, hitting IS positions in eastern Nangarhar province on Thursday.
The bombing is expected to further erode IS's capabilities in Afghanistan and sends a warning to the much bigger Taliban group ahead of their annual spring offensive.
"As a result of the bombing, key Daesh (IS) hideouts were destroyed and 36 IS fighters were killed," the Afghan defence ministry said, adding that the bombing was carried out in coordination with local military forces.
IS denied it had suffered any casualties, in a statement on its propaganda agency Amaq.
The huge bomb, delivered via an MC-130 transport plane, has a blast yield equivalent to 11 tons of TNT. It was originally designed as much to intimidate foes as to clear broad areas.
Thursday's explosion reverberated for miles and engulfed the remote area in towering flames, destroying what officials called a network of underground IS tunnels and caves that had been mined against conventional ground attacks.
A video released by the American military showed a mushroom cloud rising over the rugged terrain.
The bombardment took place amid rising global tensions as the US military steps up raids against global jihadist groups.
It comes only a week after US President Donald Trump ordered missile strikes against Syria in retaliation for a suspected chemical attack, and as China warned of the potential for conflict amid rising US tensions with North Korea.
- 'Like an earthquake' -
Trump hailed the mission in Achin district as "very, very successful".
An Afghan militant source told AFP from an undisclosed location that local people had described the ground shaking "like an earthquake", with people being knocked unconscious by the blast.
Another militant source told AFP that 800 to 1,000 IS fighters were believed to be hiding in the area, which borders Pakistan.
"Daesh (IS) fighters are active in this area and have overrun our houses," said Achin resident Khair Mohammad, welcoming the bombardment. "We don't care if our houses are destroyed, we want Daesh to be eliminated."
The arsenal was dropped after fighting intensified over the past week and US-backed ground forces struggled to advance on the area. An American special forces soldier was killed last Saturday in Nangarhar while conducting anti-IS operations.
Security experts say IS had built their redoubts close to civilian homes, but the government said thousands of local families had already fled the area in recent months of fighting.
"Precautions were taken to avoid civilian casualties," President Ashraf Ghani said on Twitter, throwing his support behind the bombardment.
- US raids surge-
But some officials close to him condemned the use of Afghanistan as what they called a testing ground for the weapon, and against a militant group that controls only a tiny sliver of territory and is not considered a huge threat.
"I find the use of the largest non-nuclear bomb, the so called 'mother of all bombs', on our soil reprehensible & counterproductive," Omar Zakhilwal, the Afghan envoy to Pakistan, said on Twitter.
"If big bombs were the solution we would be the most secure place on earth today."
But John Nicholson, the top US commander in Afghanistan, insisted it was the "right weapon against the right target".
The Pentagon's announcement of the attack drove markets down, adding to concerns among investors already wary of risks over Syria and North Korea, as well as the outcome of the French presidential election.
Trade in and out of Afghanistan from Pakistan appeared to be flowing as normal, however, with traffic at the Torkham border crossing apparently undisturbed Friday despite the historic detonation roughly 50 kilometres away.
The Taliban, who are expected to soon announce the start of this year's fighting season, condemned what it called "America's heavy use of weapons on Afghanistan".
IS, notorious for its reign of terror in Syria and Iraq, has made inroads into Afghanistan in recent years, attracting disaffected members of the Pakistani and Afghan Taliban as well as Uzbek Islamists.
But the group has been steadily losing ground in the face of heavy pressure both from US air strikes and a ground offensive led by Afghan forces.