The Taliban have seized the last major city outside of Kabul held by the country's increasingly isolated central government, cutting off the capital to the east as helicopters began landing at the US embassy there.

The collapse of Jalalabad, near a major border crossing with Pakistan, leaves Afghanistan's central government in control of just Kabul and seven other provincial capitals out of the country's 34.

In a nationwide offensive that has taken just over a week, the Taliban have defeated, co-opted or sent Afghan security forces fleeing from wide swathes of the country, even with some air support by the US military.

READ MORE: David Pratt on The World: The blame game - Washington and the West at odds over disaster in Afghanistan

The rapid shuttle-run flights near the embassy began a few hours later as diplomatic armoured SUVs could be seen leaving the area around the post.

The US government did not immediately acknowledge the movements.

However, wisps of smoke could be seen near the embassy's roof as diplomats urgently destroyed sensitive documents, according to two American military officials.

President Ashraf Ghani, who spoke to the nation on Saturday for the first time since the offensive began, appears increasingly isolated as well.

Warlords he negotiated with just days earlier have surrendered to the Taliban or fled, leaving Mr Ghani without a military option.

Ongoing negotiations in Qatar, the site of a Taliban office, have also failed to stop the insurgents' advance.

Thousands of civilians now live in parks and open spaces in Kabul itself, fearing the future.

While Kabul appeared calm on Sunday, some ATMs stopped distributing cash as hundreds gathered in front of private banks, trying to withdraw their life savings.

Militants posted photos online early on Sunday showing them in the governor's office in Jalalabad, the capital of Nangarhar province.

Abrarullah Murad, a legislator from the province, told the Associated Press that the insurgents seized Jalalabad after elders negotiated the fall of the government there.

Mr Murad said there was no fighting as the city surrendered.

The fall on Saturday of Mazar-e-Sharif, the country's fourth largest city, which Afghan forces and two powerful former warlords had pledged to defend, handed the insurgents control over all of northern Afghanistan.

Atta Mohammad Noor and Abdul Rashid Dostum, two of the warlords Mr Ghani tried to rally to his side days earlier, fled over the border into Uzbekistan on Saturday, said officials close to Dostum.

Writing on Twitter, Noor alleged a "conspiracy" aided the fall of the north to the Taliban, without elaborating.

"Despite our firm resistance, sadly, all the government and the Afghan security forces equipment were handed over to the Taliban as a result of a big organised and cowardly plot," Noor wrote.

"They had orchestrated the plot to trap Marshal Dostum and myself too, but they didn't succeed."

In his speech on Saturday, Mr Ghani vowed not to give up the "achievements" of the 20 years since the US-led invasion toppled the Taliban after the 9/11 attacks.

The US has continued holding peace talks between the government and the Taliban in Qatar this week, and the international community has warned that a Taliban government brought about by force would be shunned.

But the insurgents appear to have little interest in making concessions as they rack up victories on the battlefield.

"We have started consultations, inside the government with elders and political leaders, representatives of different levels of the community as well as our international allies," Mr Ghani said.

"Soon the results will be shared with you," he added, without elaborating further.

Many Afghans fear a return to the Taliban's oppressive rule.

The group had previously governed Afghanistan under a harsh version of Islamic law in which women were forbidden to work or attend school, and could not leave their homes without a male relative accompanying them.

Salima Mazari, one of the few female district governors in the country, expressed fears about a Taliban takeover on Saturday in an interview from Mazar-e-Sharif, before it fell.

"There will be no place for women," said Ms Mazari, who governs a district of 36,000 people near the northern city.

"In the provinces controlled by the Taliban, no women exist there anymore, not even in the cities. They are all imprisoned in their homes."

In a statement late on Saturday, however, the Taliban insisted their fighters would not enter people's homes or interfere with businesses.

They also said they would offer an "amnesty" to those who worked with the Afghan government or foreign forces.

"The Islamic Emirate once again assures all its citizens that it will, as always, protect their life, property and honour and create a peaceful and secure environment for its beloved nation," the militants said.

"In this regard, no-one should worry about their life."
Despite the pledge, those who can afford a ticket have been flocking to Kabul International Airport, the only way out of the country.