Joe Biden has warned the masterminds of a double suicide bomb attack in Kabul that killed 13 US troops and 72 Afghan civilians: “We will hunt you down and make you pay.”

On the darkest day of his presidency, Biden declined to extend his 31 August deadline for the withdrawal of US forces from Afghanistan but promised to evacuate any American citizens who want to leave.

US forces were on alert for further attacks by Islamic State, including possible rockets or vehicle-borne bombs targeting the airport, said General Frank McKenzie, head of US Central Command.

On Friday, the pace of evacuation flights accelerated, and American passport holders had been allowed to enter the airport compound, said one western security official stationed inside the airport.