Ataullah Khogyani, spokesman for the provincial governor in Nangarhar, said the number of ISIS dead was up from the 36 reported a day earlier. A Ministry of Defense official had said Friday the number of dead could rise as officials assessed the bomb site in Achin district.
"Fortunately there is no report of civilians being killed in the attack," Khogyani said.
The US attack on a tunnel complex in remote eastern Nangarhar province near the Pakistan border killed at least four ISIS leaders, Khogyani said. He said a clearance operation to assess the site of the attack was continuing.
The strike using the Massive Ordnance Air Blast bomb, or MOAB, was carried out Thursday against an ISIS tunnel complex carved into the mountains that Afghan forces had tried to assault repeatedly in recent weeks in fierce fighting in Nangarhar province.
Former Afghan president Hamid Karzai on Saturday criticized both the Afghan and US governments for the attack in Nangarhar.
Addressing a gathering in capital Kabul, Karzai said that allowing the US to carry out the bombing in Nangarhar was "a national treason" and an insult to Afghanistan.
The office of current President Ashraf Ghani said Friday there was "close coordination" between the US military and the Afghan government on the operation, and they were careful to prevent any civilian casualties.
The US estimates 600-800 IS fighters are in Afghanistan, mostly in Nangarhar.
The US has concentrated on fighting them while also supporting Afghan forces against the Taliban. There are more than 8,000 US troops in Afghanistan, training local forces and conducting counterterrorism operations.