The Taliban has seized Jalalabad without a fight, meaning Kabul is now the only big city that it does not control.
It is the latest setback for the crumbling Afghan government, which is now clinging on to the capital as its final stronghold.
The seizure of Jalalabad means the hardline Islamist group has now secured the roads that connect the country to Pakistan.
“Allowing passage to the Taliban was the only way to save civilian lives,” an Afghan official told Reuters.
The Taliban has made rapid gains over the past week, with Western countries urgently deploying troops to assist with the evacuation of diplomatic staff.
Late last night, the Taliban said that its rapid gains show that it has been popularly accepted – and attempted to reassure Afghans and foreigners, including diplomats and aid workers, that they would be safe.
“The Islamic Emirate will, as always, protest their life, property and honour and create a peaceful and secure environment for its beloved nation,” it said.
Yesterday, US President Joe Biden announced he is sending 5,000 more troops to Kabul to help remove personnel – and the evacuation of the American embassy has now begun.
His administration has warned Taliban officials any actions that put American personnel at risk “will be met with a swift and strong US military response”.
However, Mr Biden has defended his decision to withdraw US troops from the country in the coming weeks, and says the task of fighting back against Taliban insurgents must fall to Afghan forces.
He warned that an indefinite American military presence in Afghanistan is not an option, and has vowed not to pass on the war to a fifth US president.
“One more year, or five more years, of US military presence would not have made a difference if the Afghan military cannot or will not hold its own country. And an endless American presence in the middle of another country’s civil conflict was not acceptable to me,” Mr Biden said.
The president’s handling of the crisis has attracted criticism from some American politicians, with his predecessor Donald Trump claiming that Mr Biden “gets it wrong every time on foreign policy”.
In a strongly worded statement, Mr Trump said: “After I took out ISIS, I established a credible deterrent. That deterrent is now gone. The Taliban no longer has fear or respect for America, or America’s power.
“What a disgrace it will be when the Taliban raises their flag over America’s embassy in Kabul. This is complete failure through weakness, incompetence, and total strategic incoherence.”
The UK is also currently evacuating British nationals and local translators – and this weekend, 600 troops are being sent to assist with this effort.
According to The Sunday Telegraph, Britain’s ambassador to Afghanistan Sir Laurie Bristow is going to be flown out of the country by tonight.
Ben Wallace, the UK’s defence secretary, has warned it is “arrogant” to think the UK could unilaterally prevent Afghanistan falling back into the grip of the Taliban.
Afghanistan’s president, Ashraf Ghani, gave a televised speech yesterday in which he vowed not to give up on the “achievements” of the last 20 years, when US soldiers first toppled the Taliban.
Peace talks between the Taliban and the US have continued in Doha, Qatar, with warnings that a regime installed by force will not be recognised – all the while militants continue to seize control of Afghanistan.
Hundreds of people have been sleeping in tents or in the open air in Kabul, with one resident saying: “You can see the fear in their faces.”