ASAD KHEL, Afghanistan—Near the blast site of the “Mother of All Bombs,” U.S. and Afghan forces are trying to dislodge Islamic State from a mountain stronghold where the militant group recently established a new front.

Afghan commandos and U.S. Special Forces clustered with their armored vehicles on Monday by a river at the foot of the Spingar Mountains, less than a mile from where the powerful U.S. bomb struck last week. Apache helicopters and fighter jets buzzed constantly overhead, and blasts echoed across the valley.

Remains of Islamic State fighters lay strewn in the grass yards away, casualties of a battle for control of the area that began more than two weeks ago, Afghan commandos told the first journalists to arrive in Asad Khel since Thursday’s bombing. The bombing came days after an American soldier was shot in the neck and killed in a nearby village.

The bomb—often referred to by its nickname but officially called the GBU-43, or Massive Ordnance Air Blast—is one of the largest nonnuclear weapons in the U.S. arsenal and was used to target caves and tunnels in the valley beyond the village of Asad Khel.

A spokesman said the U.S. military is still assessing the damage from the bomb. An Afghan special forces commander, who was seeking shelter from the sun in a grove of trees by the river, said the bomb left a “big hole in the ground” and showed a picture of the bombing site on his phone.