Afghan president flees country after Taliban enters Kabul, a sign the government has collapsed

The takeover of the sprawling capital city had been years in the making, but was ultimately accomplished in a single day. Insurgent fighters, fresh off their conquests in each of Afghanistan's provincial hubs, faced little to no resistance as they entered the city through its major traffic arteries on Sunday morning.

By evening, the Taliban were giving television interviews in the presidential palace, just hours after Ghani had departed Afghanistan. And the Pentagon was speeding an additional 1,000 troops to Kabul's airport to assist with the withdrawal of U.S. personnel after the American flag was lowered from the embassy.

U.S. personnel at the embassy in Afghanistan were being relocated to the airport to "ensure they can operate safely and securely" as the Taliban encircled Kabul, Secretary of State Antony Blinken told ABC News on Sunday. Acting U.S. ambassador Ross Wilson was among those moved to the airport amid a frenzied rush for flights out of the country.

Asked about comparisons to the United States' departure from Vietnam in 1975, Blinken said on ABC News's "This Week" that "this is manifestly not Saigon."

Later on Sunday, the U.S. Embassy released a security alert warning of reports that the airport was taking fire and instructing U.S. citizens to shelter in place.

Ghani did not appear publicly on Sunday. But on his Facebook page, he posted a message explaining that the Taliban had given him no choice but to depart the country. "In order to avoid a flood of blood, I thought it was best to get out," he said.

Abdullah Abdullah, the head of the Afghan High Council for National Reconciliation, had earlier confirmed in a video shared online that the president was no longer in Afghanistan.

Taliban spokesman Zabiullah Mujahid initially said in a statement that the group's fighters had been instructed to stay at the entrance to Kabul, and not push further into the city with force. "We want to enter Kabul with peace, and talks are underway" with the government, he said.

But later in the day, Taliban fighters could be seen freely roaming the streets. Mujahid later wrote on Twitter that Taliban fighters had entered the city to provide security.

Footage from Al Jazeera inside the presidential palace late Sunday showed Taliban leaders with long beards and turbans seated around a wood table in the palace, as militants with guns slung across their bodies stood behind them. Some lounged on gilded chairs in the ornate building where just hours before Ghani had presided over the Afghan government.

In messages apparently distributed to Kabul residents via the messaging group WhatsApp, the group proclaimed that "we are in charge of security for Kabul." The messages listed telephone numbers in various neighborhoods where citizens should call if they saw problems.

"The Islamic Emirate assures you that no one should be in panic of feeling fear," one message said. "Taliban is taking over the city without fighting and no one will be at risk."

Meanwhile, Afghan leaders who have been the Taliban's nemesis for the past two decades issued pleas for the group to refrain from retributory violence.

Former Afghan president Hamid Karzai appeared in a video posted online, surrounded by his three daughters as a helicopter whirred overhead.

"We are trying to solve the issue of Afghanistan with the Taliban leadership peacefully," he said, according to the Associated Press.

Other figures closely associated with the American-backed government, including Gul Agha Sherzai, the former governor of Nangarhar province, recorded videos congratulating the Taliban on its victory.

One Afghan official, acting interior minister Abdul Satar Mirzakwal, said Sunday that there had been "an agreement that there will be a transitional administration for orderly transfer of power."

But Ghani's departure, apparently to a neighboring country in Central Asia with his family and much of his government, dissolved plans in place as recently as Saturday to send a team to Doha to negotiate a transition with the Taliban.

Instead, Abdullah announced the formation of a new "coordination council" with Karzai and former jihadi leader-turned-politician Gulbuddin Hekmatyar to deal directly with the Taliban in Kabul. Its purpose, Karzai said on Twitter, is to "prevent chaos ... and to better manage the affairs related to peace and the peaceful transfer" of power.

The Taliban has not responded publicly to the group, but U.S. officials assume that the militants are equally interested in preventing violence as they consolidate their control. There is no sense among those officials that a power-sharing government is being discussed. Rather, the Taliban were expected to set the terms and the council would facilitate its nonviolent takeover.

U.S. officials, focused on the evacuation, are not involved in the Afghan-to-Afghan talks.

The Taliban's lightning-quick advance to the Afghan capital came as helicopters landed at the U.S. Embassy early Sunday and armored diplomatic vehicles were seen leaving the area around the compound. Diplomats scrambled to destroy sensitive documents, sending smoke from the embassy's roof, said two State Department officials familiar with the situation.

State Department officials had preferred to evacuate the U.S. Embassy over multiple weeks, two U.S. officials told The Washington Post on Saturday. Defense officials did not think that was realistic, but waited to begin deploying additional troops to Kabul until the Biden administration made the call on Thursday to begin withdrawing. The bulk of those troops are expected to arrive by the end of the weekend, Pentagon spokesman John Kirby said on Friday.

The Pentagon is expected to deploy another 1,000 troops to Afghanistan from a brigade combat team with the 82nd Airborne Division that already was deploying to the region, two defense officials said. With the additional deployment, up to 6,000 U.S. troops could soon be on the ground at Kabul International Airport.

But meanwhile, the exit was moving forward - though in a highly precarious atmosphere.

NGO officials said they had received queries from military officials about conditions at the airport, suggesting the U.S. government was struggling to get real-time information.

Accounts circulated on social media of chaotic scenes at the airport, as foreigners and Afghans desperately sought to flee the country. A video on Snapchat showed crowds massing under a plane on the tarmac Sunday night, as people were pulled into what appeared to be a military cargo plane. In another video, posted to Twitter, a line of men with suitcases stood waiting to board an Ariana Afghan Airlines flight.

Hundreds of Afghans - including many women and children - crowded into the terminal on Sunday to wait for flights out. Cars jammed Kabul's streets as people rushed to get home or to the airport.

A U.S. defense official familiar with the situation said that no Taliban attacks have occurred on Kabul airport as of Sunday evening, but described the situation as chaotic.

Mere hours before, the Taliban had captured the city of Jalalabad, adding the eastern provincial capital to the ever-growing ranks of territory under its control. The fall came just hours after the Taliban seized Mazar-e Sharif - a northern city long seen as an anti-Taliban stronghold.

The Taliban's takeover far exceeded the pace at which the U.S. had estimated that the Afghan government could collapse. As of last week, the U.S. military had estimated a collapse within 90 days. In June, American officials had forecast that a collapse would take six to 12 months.

Blinken took to the Sunday shows to defend the Biden administration's decision to withdraw from Afghanistan, arguing that the Taliban's current offensive would have happened even if U.S. forces remained in Afghanistan.

"If the president had decided to stay, all gloves would've been off, we would've been back at war with the Taliban, attacking our forces, the offensive you've seen throughout the country almost certainly would've proceeded," Blinken told NBC News.

The Taliban's capture of Jalalabad, close to Afghanistan's border with Pakistan, came with minimal resistance after militants and local elders negotiated the fall of the city's government. Leaders in Jalalabad were given safe passage from the city, according to Reuters.

Both Bagram and Sorobi districts in Kabul province also surrendered without shots being fired, according to an official, who added that the militants had made "political deals" with local leaders.

Afghan forces on Sunday handed over Bagram air base - once the U.S. military's most important airfield in the country - to the Taliban, a district chief told the AP. The air base holds a prison housing 5,000 inmates.

The Taliban also took control of Afghanistan's largest prison, known as Pul-e-Charkhi, CNN reported, citing two unnamed Taliban sources. Up to 5,000 inmates may have been housed at the infamous prison east of Kabul, according to CNN.

Footage from an Afghan news agency on Sunday appeared to show Taliban militants letting inmates out of the prison, the BBC reported.

Several other countries that had retained a diplomatic presence in Kabul even as Taliban gains accelerated began withdrawing staff. The British ambassador will be airlifted from Afghanistan by Monday evening, the Sunday Telegraph newspaper reported. Iranian officials said its embassy in Kabul would be evacuated by Monday, according to Reuters.

Germany closed its embassy on Sunday, Reuters reported. Canada has suspended its diplomatic operations in Kabul and Canadian personnel "are now safely on their way back to Canada," the Foreign Ministry said in a statement Sunday.

The Danish and Norwegian embassies also recently said they would suspend operations and move staff out of the country.

President Joe Biden on Saturday had announced that more troops would be sent to the capital to assist the departure of Americans there, expanding the number of troops sent to Kabul to 5,000. That includes an additional 1,000 troops that had been held at the ready in Kuwait, and at least 650 who had stayed behind in Afghanistan with the mission of protecting the U.S. Embassy and airport after the United States began withdrawing its military.

The Pentagon has declined to call the deployment a combat mission. Pentagon spokesman John Kirby said troops have been deployed with machine guns, mortars and other heavy weapons with authorization to defend themselves if attacked.

Blinken was pressed by multiple television hosts Sunday about why the U.S. withdrawal appeared haphazard - particularly given the decision to withdraw forces, then send them back in. Blinken denied being caught flat-footed.

"The president was prepared for every contingency as this moved forward," he said. "We had those forces on hand and they were able to deploy very quickly again to make sure that we could move out safely."

Administration officials briefed lawmakers in two calls on Sunday morning.

In the administration's call with senators, Sen. Lindsey Graham, R-S.C., asked if the U.S. government's assessment of the terrorist threat to the United States has changed as a result of the Taliban's victory, said one Republican senator, who spoke on the condition of anonymity because of the sensitivity of the issue.

Defense Secretary Lloyd Austin had testified in June that it could take two years for an extremist group to regenerate, and assessed the likelihood of that occurring as medium.

Austin responded that the assessments have changed because of the lack of a cohesive security force on the ground. He suggested he could provide a more complete answer in a classified setting, the senator said.

Austin also said that the military will run as many aircraft as it can to rescue people, with American embassy workers at the front of the list. Afghans with still-processing special immigrant visas would be next, followed by others who seek to come to the United States through other categories.

Aerial refueling will limit how much fuel is needed on the ground when using military aircraft, the senator added.

"It sounds like they're going to try to get as many out as possible, but with the situation deteriorating so rapidly, our question that is largely unanswered is how long can this sustain, and how many people will we actually get out?" the senator said. "We really don't know that."

British lawmakers will also be recalled from recess next week to discuss the "deteriorating situation in Afghanistan," Sky News reported.

Biden has warned that any moves by the Taliban that threaten American personnel or interests in the country would face a "swift and strong" response by the U.S. military.

The fall of Mazar-e Sharif on Saturday came as the Taliban gained control of the province of Logar, an important gateway to the capital. Militants on Saturday also captured the capital of Paktika, an eastern province bordering Pakistan, where local leaders fled for Kabul after surrendering.

As the Taliban had advanced toward Kabul in recent days, the capital was overrun by Afghans fleeing oppressive militant rule amid fears of a humanitarian disaster. Families who had flocked to Kabul were selling their possessions in an attempt to raise money as reports spread that ATMs had stopped dispensing cash.

At the airport, people who had provided help to Western governments were seen on television news footage swarming visa processing centers, seeking a way out of the country. "We served for the American forces," one person at the airport told ABC News. "They have to take care (of) us. It is our turn to be helped."