WASHINGTON, Aug 19 (CGTN) - The U.S. has airlifted about 7,000 people out of Afghanistan since the evacuation mission started on August 14, the Pentagon said on Thursday.

In the past 24 hours alone, over 2,000 people were evacuated on C-17 aircraft, about 300 of whom were Americans.

More than 5,200 U.S. troops are now at Kabul airport to guard the evacuation, as well as armed fighter jets flying over Kabul to ensure security for the evacuation operation.

But Pentagon spokesman John Kirby told reporters on Thursday that he doesn't know how many U.S. citizens are still left in Afghanistan.