WATCH: Pentagon spokesperson John Kirby and Gen. Frank McKenzie hold briefing on Afghanistan

WASHINGTON — The U.S. 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.

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

He 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.

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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.

On Thursday, Pentagon spokesperson John Kirby confirmed on Twitter that there was an explosion outside the Kabul airport.