(NEXSTAR) — The United States general overseeing the evacuation from Afghanistan says the United States will “go after” the perpetrators of the Kabul airport attacks if they can be found.

Gen. Frank McKenzie said during a briefing Thursday the attacks were believed to have been carried out by fighters associated with the Islamic State group’s Afghanistan affiliate.

The IS branch, known as The Islamic State-Khorasan Province after a name for the region from antiquity, later claimed credit for the attack and said it targeted American troops and their Afghan allies.

The statement carried a photo of what the militant group said was the bomber who carried out the attack. The image shows the alleged attacker standing with the explosive belt in front of the black IS flag with a black cloth covering his face, only his eyes showing.

The statement made no mention of a second suicide bomber or gunmen. The claim could not be independently verified.

IS also said the bomber managed to get past Taliban security checkpoints to come within 5 yards of a gathering of U.S. soldiers, translators and collaborators before detonating his explosives. It said Taliban were also among the casualties. The extremist IS group has battled the Taliban, which it views as traitorous for agreeing to a peace deal with the United States.

Gen. McKenzie said the attacks, which killed 12 U.S. service members, would not stop the United States from continuing its evacuation of Americans and others. McKenzie warned there are still “extremely active” security threats at the airport in the Afghan capital.

“We expect these attacks to continue,” he said, adding that Taliban commanders have been asked to take additional security measures to prevent another suicide bombing on the airport’s perimeter. He said he sees no indication that the Taliban allowed Thursday’s attacks to happen.

McKenzie said the U.S. is sharing some information with the Taliban in hopes of preventing future violence.

“We share versions of this information with the Taliban so that they can actually do some searching out there for us, and we believe that some attacks have been thwarted by them, ” said McKenzie, referencing the range of perceived threats. “We cut down the information we give the Taliban, they don’t get the full range of information we have. But we give them enough to act in time and space.”

Also Thursday, Defense Secretary Lloyd Austin suggested the evacuation will go on and expressed his “deepest condolences to the loved ones and teammates of all those killed and wounded in Kabul today.”

“Terrorists took their lives at the very moment these troops were trying to save the lives of others,” he said. “We mourn their loss. We will treat their wounds. And we will support their families in what will most assuredly be devastating grief. But we will not be dissuaded from the task at hand.”

“To do anything less — especially now — would dishonor the purpose and sacrifice these men and women have rendered our country and the people of Afghanistan,” the statement also said.

At least 60 Afghans and 12 U.S. troops were killed Thursday, Afghan and U.S. officials said. More were reported injured.

The Associated Press contributed to this report.