“We will not forgive, we will not forget, we will hunt you down and make you pay,” were the words of a sombre Joe Biden following Thursday’s attacks in Kabul.

Addressing the nation, the president paid tribute to those who lost their lives in a terrorist incident outside Hamid Karzai International Airport amid the evacuation of Western civilians and Afghan refugees. At the latest count, at least 100 people have been killed after three blasts and gunfire outside the airport, according to Taliban officials. Among the fatalities were 13 US personnel, including 12 Marines. Around 143 people, 15 of whom are American soldiers, are being treated for injuries. The Islamic State Khorasan Province, or Isis-K, has taken responsibility for the incident.

Biden described the murdered American personnel as “heroes” who were “engaged in a dangerous, selfless mission to save the lives of others”. During the press conference, he said: “The intelligence community has assessed an attack by a group known as Isis-K took the lives of American service members standing guard at the airport and wounded several others seriously.

“With regard to finding, tracking down, the Isis leaders who ordered this, we have some reason to believe we know who they are, we are not certain, and we will find ways of our choosing, without large military operations, to get them wherever they are.”

General Frank McKenzie commented after the attacks: “If we can find who is associated with this, we will go after them.”

Pressure is mounting on the president over his decision to pull troops of the country after nearly two decades of involvement. The president has vowed to complete the evacuation of its citizens. More than 100,000 people have been evacuated from Afghanistan, but Secretary of State Antony Blinken has briefed that around 1,500 Americans remain stranded as the rapidly approaching 31 August withdrawal deadline nears. Some Republicans are lobbying White House officials for flights to continue beyond next Tuesday.

Across the Atlantic, prime minister Boris Johnson – who described the attack as “despicable” – chaired an emergency response meeting and said the evacuation project for British passport holders and eligible Afghans will continue.