Several US service members were also killed in the attack that was carried out by the terror group ISIS-K.

The Department of Homeland Security is tracking three primary threats, including whether individuals abroad in Afghanistan, who are associated with ISIS or al Qaeda, could use the relocation process as a way to enter the US, according to a federal government call with law enforcement partners last Friday, obtained by CNN.

"To counteract that, there's an extensive screening and vetting process that is in place for those who are being relocated to the United States," DHS Intelligence chief John Cohen said on the call.

As the last US military flight carrying troops left the Hamid Karzai International Airport (HKIA) in Kabul, the United States completed the withdrawal of its forces from Afghanistan, ending a two-decade-long war ignominiously, with the Islamist Taliban in full control.

The last three US military evacuation flights departed HKIA just ahead of the August 31 deadline. The last one, a C-17 Globemaster transport plane, took off from the Kabul airport at 3:29 pm. East Coast Time, Russia Today (RT) reported quoting General Kenneth McKenzie, head of the US Central Command (CENTCOM).