"The former Afghan president has left the nation," Abdullah Abdullah, who heads the peace process, said in a video on his Facebook page.

"He left Afghanistan in a hard time, God hold him accountable," Abdullah said.

In a stunning rout, the Taliban seized nearly all of Afghanistan in just over a week, despite the billions of dollars spent by the US and NATO over nearly two decades to build up Afghan security forces. Just days earlier, an American military assessment estimated it would be a month before the capital would come under insurgent pressure.

Instead, the Taliban swiftly defeated, co-opted or sent Afghan security forces fleeing from wide swaths of the country, even though they had some air support from the US military.