KABUL (AFP) - Afghan President Ashraf Ghani flew to the besieged northern city of Mazar-i-Sharif on Wednesday (Aug 11) to rally his beleaguered forces, with Taleban fighters having now taken more than a quarter of the country's provincial capitals in less than a week.

Mr Ghani arrived in Mazar as the Taleban captured Faizabad overnight, making it the ninth city to be overrun since last Friday.

He plans "to check the general security in the northern zone", according to a statement released by the palace.

The Afghan leader was also likely to hold talks with Mazar's long-time strongman Atta Mohammad Noor and infamous warlord Abdul Rashid Dostum about the defence of the city, as Taleban fighters inched closer to its outskirts.

The loss of Mazar would be a catastrophic blow to the Kabul government and represent the complete collapse of its control over the north - long a bastion of anti-Taleban militias.

Hours before Mr Ghani arrived, pictures posted on official government social media accounts showed Mr Dostum boarding a plane in Kabul, along with a contingent of commandos, en route to Mazar.

Fighting in Afghanistan's long-running conflict has escalated dramatically since May, when the United States-led military coalition began the final stage of a withdrawal set to be completed before the end of the month.

Further to the east of Mazar in Badakhshan's capital Faizabad, a local lawmaker told AFP that security forces had retreated after days of heavy clashes.

"The Taleban have captured the city now," said Zabihullah Attiq.

The insurgents also confirmed in a social media post that their fighters were in control of the city.

But even as the Taleban routed government forces, US President Joe Biden gave no hint of delaying his deadline to withdraw all American troops by Aug 31, instead urging Afghan leaders to "fight for themselves" on Tuesday.

"I do not regret my decision" to withdraw US troops after two decades of war, he told reporters in Washington.

And as fighting raged, US diplomats were desperately trying to breathe life back into all but dead talks between the Afghan government and Taleban in Doha, where Washington's special envoy Zalmay Khalilzad was pushing the Taleban to accept a ceasefire.

Mr Biden has stressed that Washington would continue to support the Afghan security forces with air strikes, food, equipment and money for salaries.

"They have got to want to fight. They have outnumbered the Taleban," he said.

The Taleban have appeared largely indifferent to peace overtures, and seem intent on a military victory to crown a return to power after their ouster 20 years ago in the wake of the Sept 11 attacks.

After conquering most of the north, the Taleban have now set their sights on the region's biggest city, Mazar-i-Sharif - long a linchpin for the government's control of the area - after capturing Sheberghan to its west, and Kunduz and Taloqan to its east.

Government forces are also battling the hardline Islamists in Kandahar and Helmand, the southern Pashto-speaking provinces from where the Taleban draw their strength.