The Taliban have entered the outskirts of the capital Kabul, three Afghan officials said.
The militant group has already seized all major cities apart from Kabul - as the US and UK deploy personnel to support evacuation efforts.
The Taliban have said in a statement they do not plan to take the capital "by force".
Sunday morning's collapse of Jalalabad, near a major border crossing with Pakistan, leaves Afghanistan’s central government in control of just Kabul and six other provincial capitals out of the country’s 34.
It comes as around 600 British personnel have deployed to the country to support the evacuation of British Nationals from Afghanistan and aid the evacuation of former British staff eligible for relocation under the Afghan Relocation and Assistance Policy (ARAP).
Writing in The Telegraph, UK Defence Secretary Ben Wallace warned it is "arrogant" to think the UK could unilaterally prevent Afghanistan falling back into the grip of the Taliban, adding that there was little more Britain could have done in the "absence of international allies".
Afghanistan faces a "catastrophic" humanitarian disaster if action is not taken to prevent the country’s collapse in the face of the Taliban advance, the chairman of the Commons Defence Committee has warned.
Tory MP Tobias Ellwood told Times Radio: "This is completely humiliating for the West. We assembled the most incredible, technologically advanced alliance the world has ever seen and we are being defeated by an insurgency that’s armed with AK47s and RPGs.
"This will be the biggest own goal made by the West so far this century.
"The humanitarian disaster that is about to unfold will be catastrophic, the migration challenges will be huge. We will see further terrorist attacks."
Cover image: Kabul, Afghanistan (Picture: Alamy).