The Taliban has captured the last major city in northern Afghanistan which was still under government control, local officials said on Saturday.
Militant fighters have taken Mazar-e-Sharif, meaning they now control most of local capitals and are edging closer to the capital Kabul.
More than 250,000 people have already thought to have been displaced, with many fleeing to the capital to escape the violence.
About 600 British troops are due to arrive in the city to help with the withdrawal of UK citizens and assist with the relocation of Afghans who have helped allied forces and risk reprisals from the Taliban.
US troops in Kabul will be able to airlift thousands of people a day to safety, officials said.
Other Western countries are now scrambling to evacuate their citizens while scaling back their presence in the country and, in some cases, closing their embassies.
Women in Taliban controlled areas have described being forced to wear burkas, while there have been reports of public beatings and lashings of people who break social rules.
A number of cities have negotiated surrenders with the Taliban as government forces crumble. However, there is no sign of that happening in Kabul.
The capitals of two more provinces, Paktika and Kunar, fell to the militants on Saturday.
Footage from the city of Assadabad, in Kunar, appeared to show people waving the Taliban flag and walking through the streets.
Local officials said the northern city of Mazar-e-Sharif - the fourth largest in Afghanistan - fell without a fight on Saturday.
"The Taliban have taken control of Mazar-e-Sharif," Afzal Hadid, head of the Balkh provincial council, told Reuters news agency.
He added that soldiers abandoned their equipment and headed towards the Uzbekistan border.
President Ashraf Ghani said the top priority was the remobilisation of the Afghan armed forces to prevent the further displacement of people.
In pre-recorded TV address he would not let a war that was "imposed" on people "cause more deaths”.
