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The massive bomb used by the United States against a base in eastern Afghanistan destroyed a tunnel complex built almost four decades ago by Islamist fighters during the Soviet invasion of the Asian country, Afghan officials said on Friday.

The intricate web of tunnels and caves was located under a base now belonging to the Islamic State terror organization, which improved and expanded the system in a mountainous region of the Momand Valley in the Nangarhar province.

The entirety of this underground complex, which spanned 300 meters (984 feet), was completely destroyed when the US dropped its 10-ton Massive Ordnance Air Blast (GBU-43/B) on it, according to the government’s media and information center.

Zabihullah Zmarai, the deputy head of Nangarhar’s provincial council, told EFE that the ‘Mujahideens’ (jihadist guerrilla fighters) had built bunkers and tunnels in caves in the area after the USSR’s invasion of Afghanistan in 1979.

He explained that the tunnels extended throughout the valley and connected mountains through a maze-like system of subterranean passages.

In the past two years, when the IS first started to operate in Afghanistan, the terror group began to dig additional tunnels and reinforced the old system to make it more resistant to airstrikes.

Zmarai, who has often taken part in the Afghan forces’ field operations, told EFE that “small bombs were not able to destroy Daesh’s (another name for the IS) caves and tunnels.”

“Therefore, the big bomb was used and that was our hope: to use such bombs to eliminate Daesh’s leadership,” Zmarai added.

The GBU-43 has been touted by the US military as the most powerful conventional (non-nuclear) bomb ever designed.

“The mother of all bombs was used in Achin against the Daesh base after several aerial and ground offensives by Afghan and foreign forces failed to clear the area,” Attaullah Khogyanai, a spokesman for the governor of Nangarhar, told EFE.

According to Khogyanai, dozens of drone strikes had been ineffective, and at least three ground offensives by the Afghan army and foreign troops had failed to clear the IS base.

“Now our forces will be able to easily deal with the challenges in this area,” he added.

Khogyanai’s comments appeared to contradict the information released by the Afghan government in June 2016, when it said that the IS no longer posed a threat to national security as it had been wiped out in most of the areas in which it was active in the country.

The Afghan government said earlier this week that fewer than 400 IS insurgents remained in only two of the 34 provinces in the country after 2,500 members were killed last year.

Below is footage of a large bomb used in Yemen in 2014 with a blast similar to that of the MOAB used in Afghanistan on April 13 2017.

© 2017 EFE News Services (U.S.) Inc.