Singapore: The head of Afghanistan's central bank has fled Kabul, questioned the loyalty of Afghan security forces and blamed President Ashraf Ghani and his inexperienced advisors for the country's swift and chaotic fall to the Taliban.

In a Twitter thread on Monday detailing how he worked at the bank until terrorists were at the gates of the city, Acting Governor Ajmal Ahmady also said that US dollar supplies were dwindling and described escaping the capital on a military flight.

"On Sunday, I began work. Reports throughout morning were increasingly worrisome. I left the bank and left deputies in charge. Felt terrible about leaving staff," he said.

"It did not have to end this way. I am disgusted by the lack of any planning by Afghan leadership. Saw at airport them leave without informing others."

Ghani fled Afghanistan on Sunday as Taliban terrorists entered Kabul virtually unopposed.

Their arrival, barely a week after they captured faraway provincial capital Zaranj, was disorienting, said Ahmady, 43.

He was appointed acting governor of Afghanistan's central bank just over a year ago, having previously worked at the US Treasury, the World Bank and in private equity, according to a short biography posted on a government website.

"Seems difficult to believe, but there remains a suspicion as to why (Afghan National Security Forces) left posts so quickly," Ahmady said, referring to claims by some pro-government militia leaders of that the army's capitulation in northern Afghanistan was the result of a conspiracy.

"There is something left unexplained."

Ahmady did not respond to Reuters' emails and messages seeking comment. His remarks were posted from his verified Twitter account. A World Bank source who has been in correspondence with Ahmady said the account was genuine.