The United States has dropped its “largest non-nuclear bomb” on what it says were the Islamic State group’s hideouts in Nangarhar, Afghanistan, a spokesperson for the Pentagon said on Thursday. The weapon weighed 11 tonnes and was used in combat for the first time, according to ABC News.

The weapon, which was code-named the “Mother of All Bombs”, was dropped out of the back door of a MC-130 military transport aircraft. Officials told CNN that MOAB was dropped at 7 pm local time. Nangarhar is located close to the Afghanistan-Pakistan border.

Military officials said the Islamic State group’s tunnels and fighters in Nangarhar province’s Achin district were targeted. The commander of the US military in Afghanistan, General John Nicholson, had authorised the operation, and US forces are assessing the damage, officials said. Though US has not yet confirmed the results of the strike, a local official told BBC that several militants were killed.

General Nicholson said the extremist outfit was using IEDs, bunkers and tunnels to “thicken their defence”. “This [MOAB] is the right munition to reduce these obstacles and maintain the momentum of our offensive,” he said, adding that US forces had “taken every precaution to avoid civilian casualties”.

At a White House press briefing, Press Secretary Sean Spicer said the US military “targeted a system of tunnels and caves that Islamic State fighters used to move around freely and attack US and Afghan forces in the area”. “US takes the fight against ISIS very seriously to defeat them. We must deny them operational space,” he said, adding that the military took “all precautions necessary to prevent civilian casualties and collateral damage”.

The bomb used, according to Reuters, was the GBU-43/B Massive Ordnance Air Blast. This GPS-enabled munition was first tested in March 2003 in Florida and was believed to have been developed as part of the Iraq War campaign. This is the first time it been deployed outside of a testing situation.

US President Donald Trump said the “very successful mission” was proof of his powerful foreign policy, reported Reuters. “If you look at what’s happened over the last eight weeks and compare that really to what’s happened over the last eight years, you’ll see that there’s a tremendous difference,” he said from the White House on Thursday.

One of Trump’s key poll planks was to fight the Islamic State group. The Afghanistan strike comes about a week after the US ordered a missile attack on a Syrian government airbase in response to a deadly chemical attack in the country, believed to have been launched by Bashar al-Assad’s forces, which left dozens dead.