Taliban fighters sit over a vehicle on a street in Laghman province on August 15, 2021.

AFP | Getty Images

WASHINGTON – Taliban fighters began entering the Afghan capital, Kabul, the last city so far spared militant takeover when they quickly captured the country following the withdrawal of US forces.

A Taliban spokesman said the fighters wanted to negotiate a “peaceful surrender” of the city.

“Until a peace agreement is reached, the security of the city and its residents is the responsibility of the government and it should guarantee it,” Taliban spokesman Zabihullah Mujahid said in a statement.

Two U.S. defense officials confirmed to NBC News that the Taliban also seized Bagram Air Force Base, a development that came less than two months after the U.S. military handed over the once steadfast air base to the Afghan National Security and Defense Forces.

The group began emptying the local Parwan Prison, which is estimated to have 5,000 to 7,000 prisoners, including die-hard Taliban and Al-Qaeda militants, officials said, who spoke on condition of anonymity.

In 2012, at its peak, Bagram looked through more than 100,000 U.S. soldiers. It was the largest US military facility in Afghanistan.

Since President Joe Biden’s decision in April to withdraw US forces from Afghanistan, the Taliban have made breathtaking strides on the battlefield, with almost the entire nation under their control.

The group had previously captured the strategic city of Ghazni, which had its front line within 95 miles of Kabul, a staggering development that prompted 5,000 American troops to be sent into the country to aid in evacuations.

Britain and Canada also stormed troops into Kabul to evacuate their embassies.

The State Department repeatedly urged US citizens to leave Afghanistan immediately, warning that its ability to help citizens was “extremely limited” due to deteriorating security conditions and downsizing.

A U.S. Chinook helicopter overflies the city of Kabul, Afghanistan on Sunday, August 15, 2021. Taliban fighters invaded the outskirts of the Afghan capital and further increased their hold in the country as panicked workers fled government offices and helicopters landed at the U.S. embassy.

Rahmat Gül | AP

Although the Afghan military, long backed by US and coalition forces, outnumbered them, last week the Taliban captured Kandahar and Herat, Afghanistan’s second and third largest cities. The group also captured the strategic city of Pul-e-Alam, a city that has one of the four main roads into Kabul.

Continue reading: Afghanistan’s war will spread beyond its borders as the Taliban advance, a senior negotiator warns

The Pentagon previously stated that the ongoing Taliban offensive across the country violates a commitment made by the group last year to open peace talks with the Afghan government.

The peace talks taking place in Qatar have now stalled.

“What we are seeing on the ground is that the Taliban are advancing and taking control of district and provincial centers, which clearly shows that they believe it is possible to get government through violence, brutality, violence and repression in great contradiction to their previously stated goal of actually participating in a negotiated political solution, “Pentagon spokesman John Kirby recently told reporters.

Taliban troops patrol a street in Herat, Afghanistan on August 14, 2021.

Stringer | Reuters

He added that while the Pentagon is concerned to see such advances by the Taliban, the Afghan military must now take advantage of nearly two decades of training from US and NATO coalition forces.

“They have the advantage in numbers, operational structure, air force and modern weapons, and it’s really about having the will and leadership to use those advantages for their own benefit,” said Kirby.

“The recipe cannot just be a permanent US presence in Afghanistan that never ends,” he added.

Last week, Biden told reporters at the White House that he had no regrets about his decision to withdraw American troops from Afghanistan, despite the Taliban’s shocking gains.

“Look, we’ve spent over a trillion dollars over 20 years, we’ve trained and equipped over 300,000 Afghan forces with modern equipment,” Biden said.

“Afghan leaders need to come together,” added the president. “You have to fight for yourself, fight for your nation.”

CNBC’s Natasha Turak contributed to this report from Dubai, United Arab Emirates.