US drops the "mother of all bombs" on Islamic State.

The United States have dropped “the mother of all bombs,” the largest non-nuclear device it has ever unleashed in combat, on a network of caves and tunnels used by Islamic State in eastern Afghanistan, the military said.

President Donald Trump touted the bombing on Thursday as evidence of a more muscular US foreign policy since he took office in January after eight years of President Barack Obama.

The 10-ton GBU-43 bomb was dropped from a MC-130 aircraft in the Achin district of Nangarhar province, close to the border with Pakistan, Pentagon spokesman Adam Stump said.

The GBU-43, also known as the “mother of all bombs,” is a GPS-guided munition and was first tested in March 2003. It is regarded as particularly effective against clusters of targets on or just underneath the ground.

It was the first time the United States has used this size of conventional bomb in a conflict.

Trump described the bombing as a “very successful mission.” It was not immediately clear how much damage the device did.

During last year’s presidential election campaign, Trump vowed to give priority to destroying Islamic State, which operates mostly in Syria and Iraq. He flexed US military muscles last week by ordering a cruise missile attack on a Syrian government airbase in retaliation for a poison gas attack.

“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,” Trump told reporters at the White House on Thursday.

The security situation remains precarious in Afghanistan, with a number of militant groups trying to claim territory more than 15 years after the US invasion which toppled the Taliban government.

So far, Trump has offered little clarity about a broader strategy for Afghanistan, where some 8400 US troops remain.

Last week, a US soldier was killed in the same district as where the bomb was dropped while he was conducting operations against Islamic State.