WASHINGTON: The US Department of Defence said on Friday that `the mother of all bombs` targeted a base in Afghanistan of the militant Islamic State of Khorasan (ISK) group, which draws most of its fighters from the banned Tehreel(-i-Taliban Pakistan (TTP).

According to a Pentagon media release, ISK, also known as the Khorasan group, is based in the `Afghanistan-Pakistan region` and is composed primarily of former members of TTP and the Afghan Taliban.On Thursday, a US aircraft dropped the American military`s biggest non-nuclear bomb on Afghanistan and President Donald Trump praised the strike as a `very, very successful mission` Better known as the `mother of all bombs`, the weapon is officially known as the GBU-43/B Massive Ordnance Air Blast (MOAB).

The Afghan defence ministry said the massive bomb killed 36 ISK militants and destroyed their base and that no civilians were harmed in the attack.

`As a result of the bombing, key Daesh [ISK] hideouts were destroyed and 36 IS fighters were killed,` the ministry said, adding that the bombing was carried out in coordination with local military forces. However, former Afghan president HamidKarzai, who supports maintaining TTP camps in Afghanistan, condemned the attack as `an inhuman and most brutal misuse of our country`.

The Pentagon said the strike targeted an ISK tunnel complex in Achin district of Nangarhar province and was part of ongoing efforts to defeat the group in Afghanistan. The aim was to minimise the risk to be faced by the Afghan and US forces carrying out clearing operations in the area while maximising the destruction of ISK fighters and facilities.

At a news briefing on Wednesday, President Trump indicated that he had given the Pentagon a free hand to use the weapon as part ofhis pledge to step up the war on IS. `We have given them total authorisation and that`s what they`re doing and franklythat`s why they`ve been so successful lately,` he said.

`This is the right munition to reduce these obstacles and maintain the momentum of our offensive against ISIS-K [ISK],` said Gen John W.

Nicholson, the commander of all US and Nato forces in Afghanistan.

`US forces took every precaution to avoid civilian casualties with this strike and will continue offensive operations until ISIS-K [ISK] is destroyed in Afghanistan, the statement added.

Gen Nicholson told the US Senate Armed Services Committee in February that TTP provided the core fighting group for ISK and most of these fighters came from the Orakzai tribal region.

He also said that TTP militants from the agency movedinto Afghanistan`s Nangarhar province after joining ISK and based themselves in the area that was bombed on Thursday.

`The majority of the fighters in the ISK right now came from TTP, the Pakistani Taliban, who had carried out dozens of attacks inside Pakistan, Gen Nicholson said.

Military experts appearing on various US television channels said the bomb dropped at the ISK tunnel complex was 30 feet long, weighed 21,600 pounds and was packed with 18,000 pounds of explosives.

CNN military analyst Rick Francona said the bomb was used because it could create `a blast effect into the caves and tunnels`, sending shock waves through the tunnel systems and killing `almost everybody in there within a certain range`.