KABUL, Afghanistan (AP) Two suicide bombers and gunmen attacked crowds of Afghans flocking to Kabuls airport Thursday, transforming a scene of desperation into one of horror in the waning days of an airlift for those fleeing the Taliban takeover. The attacks killed at least 60 Afghans and 13 U.S. troops, Afghan and U.S. officials said.

The U.S. general overseeing the evacuation said the attacks would not stop the United States from evacuating Americans and others, and flights out were continuing. Gen. Frank McKenzie, head of U.S. Central Command, said there was a large amount of security at the airport, and alternate routes were being used to get evacuees in. About 5,000 people were awaiting flights on the airfield, McKenzie said.

The blasts came hours after Western officials warned of a major attack, urging people to leave the airport. But that advice went largely unheeded by Afghans desperate to escape the country in the last few days of an American-led evacuation before the U.S. officially ends its 20-year presence on Aug. 31.

The Islamic State group claimed responsibility for the killings on its Amaq news channel. The IS affiliate in Afghanistan is far more radical than the Taliban, who recently took control of the country in a lightning blitz. The Taliban were not believed to have been involved in the attacks and condemned the blasts.

In an emotional speech from the White House, U.S. President Joe Biden said the latest bloodshed would not drive the U.S. out of Afghanistan earlier than scheduled, and that he had instructed the U.S. military to develop plans to strike IS.

We will not forgive. We will not forget. We will hunt you down and make you pay, Biden said.

U.S. officials initially said 11 Marines and one Navy medic were among those who died. Another service member died hours later. Eighteen service members were wounded and officials warned the toll could grow. More than 140 Afghans were wounded, an Afghan official said.

One of the bombers struck people standing knee-deep in a wastewater canal under the sweltering sun, throwing bodies into the fetid water. Those who moments earlier had hoped to get on flights out could be seen carrying the wounded to ambulances in a daze, their own clothes darkened with blood.