The United States on Monday completed its military withdrawal from Afghanistan after a huge but chaotic airlift that cost the lives of 13 US troops and left behind thousands of Afghans and hundreds of Americans still seeking an escape from Taliban rule.

In a first in the nearly 20 years since al Qaeda's Sept 11, 2001, attacks plunged the United States into war, not a "single service member" from the US military was in Afghanistan, the Pentagon said in an afternoon news conference.

"Heartbreak" was the word that US Marine General Frank McKenzie used as he described emotions surrounding the US departure from its longest war after dangerous and tireless efforts by US troops to evacuate American citizens and vulnerable Afghans.

"There's a lot of heartbreak...