Former Afghan President Ashraf Ghani, who fled Kabul as Taliban forces reached the outskirts of the city last month, apologised on Wednesday for the abrupt fall of his government but denied that he had taken millions of dollars with him.

In a statement posted on Twitter, Ghani said he had left at the urging of his security team who said that if he stayed there was a risk of "the same horrific street-to-street figting the city had suffered during the Civil War of the 1990s."

"Leaving Kabul was the most difficult decision of my life, but I believed it was the only way to keep the guns silent and save Kabul and her 6 million citizens," he said.

The statement largely echoed a message Ghani sent from the United Arab Emirates in the immediate aftermath of his departure, which drew bitter criticism from former allies who accused him of betrayal.

Ghani, a former World Bank official who became president after two bitterly disputed elections marred by widespread allegations of fraud on both sides, dismissed reports that he had left with millions of dollars in cash as "completely and categorically false."

"Corruption is a plague that has crippled our country for decades and fighting corruption has been a central focus of my efforts as president," he said, adding that he and his Lebanese-born wife were "scrupulous in our personal finances."

He offered appreciation for the sacrifices Afghans had made over the past 40 years of war in their country.

"It is with deep and profound regret that my own chapter ended in similar tragedy to my predecessors - without ensuring stability and prosperity. I apologize to the Afghan people that I could not make it end differently."