The Taliban government has killed the alleged mastermind of a devastating suicide bomb attack at the Kabul airport during the chaotic withdrawal of US forces in 2021, the White House said Tuesday.

The bomber detonated among packed crowds at the airport’s perimeter as they tried to flee Afghanistan on August 26, 2021. The blast killed some 170 Afghans and 13 US troops who were securing the airport for the traumatic exit.

It was one of the deadliest bombings in Afghanistan in recent years, and prompted a wave of criticism of President Joe Biden for his decision to pull American forces out of the country nearly 20 years after the US invasion.

The leader of the Islamic State cell that planned the attack was killed by Taliban authorities, White House national security spokesman John Kirby said in a statement.

“He was a key ISIS-K official directly involved in plotting operations like Abbey Gate, and now is no longer able to plot or conduct attacks,” Kirby said, referring to the spot outside the airport where the attacks took place.

ISIS-K refers to Islamic State Khorasan, the branch of the group operating in Afghanistan and Pakistan.

“He was killed in a Taliban operation,” Kirby added without giving any details of it.

The pullout, ending on August 30, 2021, saw Taliban fighters sweep aside Western-trained Afghan forces in just weeks, forcing the last US troops to mount the desperate evacuation from Kabul’s airport.

An unprecedented military airlift operation managed to get more than 120,000 people out of the country in a matter of days.

Biden has long defended his decision to leave Afghanistan, which critics have said helped cause the catastrophic collapse of Afghan forces and paved the way for the Taliban to return to power two decades after their first government was toppled.

Nothing “would have changed the trajectory” of the exit and “ultimately, President Biden refused to send another generation of Americans to fight a war that should have ended for the United States long ago,” the White House National Security Council said in a report to Congress earlier this month.

A recent Washington Post report citing leaked Pentagon documents said the United States believes that since the withdrawal, Afghanistan is becoming a “staging ground” for the Islamic State group.

In his statement, Kirby said Tuesday, “We have made clear to the Taliban that it is their responsibility to ensure that they give no safe haven to terrorists, whether Al-Qaeda or ISIS-K.”

He added: “We have made good on the President’s pledge to establish an over-the-horizon capacity to monitor potential terrorist threats, not only from Afghanistan but elsewhere around the world where that threat has metastasized, as we have done in Somalia and Syria.”

The Taliban and IS have long engaged in a turf war in Afghanistan, and experts have pointed to the jihadist group as the biggest security challenge for the new Afghan government going forward.