The Taliban are gaining territory across Afghanistan at a stunning pace and have reportedly taken the key cities of Herat, Kandahar and Ghazni in quick succession.
The loss of Kandahar and Herat, Afghanistan's second- and third-largest cities, would mark a devastating blow to President Ashraf Ghani and calls into urgent question how long he can cling to power.
Situated about 150 kilometres from Kabul along the Kabul-Kandahar highway, Ghazni serves as a gateway from the capital to the Taliban's strongholds in the south. Its fall on Thursday marked the 10th provincial capital to be taken by the Taliban this week.
In Herat to the east and Kandahar to the south, Taliban forces reportedly swept into the key cities, capturing police and military headquarters.
“Kandahar is completely conquered. The Mujahideen reached Martyrs' Square in the city,” a Taliban spokesman tweeted on an officially recognised account — a claim backed by a resident, who told AFP that government forces appeared to have withdrawn en masse to a military site outside the city.
A doctor based in southern Kandahar said the city was receiving scores of bodies of Afghan forces, and some injured Taliban fighters were also seeking medical support. The fighting was extremely intense in Kandahar city, he said, with constant rocket attacks.
All roads to Kabul, which lies in a valley surrounded by mountains, were choked with civilians fleeing violence elsewhere, a western security source there said.
It was hard to tell whether Taliban fighters were also coming through, the source said.
In Ghazni, the Taliban took control of key areas including, the governor's office, police headquarters and the prison, Nasir Ahmad Faqiri, head of the provincial council, told AFP.
He said the fighting continued in parts of the city but the provincial capital was largely in the hands of the insurgents. The Taliban also confirmed the capture the city, their representative said.
Ghazni's governor, Dawood Laghmani, was arrested along with his colleagues by security forces, Interior Ministry spokesman Mirwais Stanekzai said.
Mr Laghmani's arrest came after he had left the province for Kabul.
The Taliban also reportedly took over the police headquarters in Herat, Afghanistan's third-largest city.
An AFP correspondent filmed the Taliban flag flying over the police headquarters in Herat while the insurgents tweeted: “The enemy fled … Dozens of military vehicles, weapons and ammunition fell into the hands of the Mujahideen.”
Further details of the Taliban's presence in the city were not immediately available, but it has been under siege for weeks.
Herat — about 125 kilometres from the Iranian border — is home to veteran warlord Ismail Khan, who for weeks has been rallying his forces to make a stand against the Taliban.
Recent US military intelligence has shown the Taliban could take Kabul within 90 days.
A US military official told Reuters the new assessment of how long Kabul could stand was a result of the Taliban's rapid gains as US-led foreign forces leave.
“But this is not a foregone conclusion,” the official added, saying the Afghan security forces could reverse the momentum by putting up more resistance.
The takeover of Ghazni will add further pressure on the country's already overstretched air force, needed to bolster Afghanistan's scattered security forces that have increasingly been cut off from reinforcements by road.
The Taliban now control 65 per cent of Afghanistan and have taken or threaten to take 11 provincial capitals, a senior EU official said on Tuesday.
The US and Britain are temporarily sending a combined total of 3,600 troops to Afghanistan to enable “the safe and orderly departure” of diplomats and others as the Taliban continue a blitz across the country and set their sights on Kabul, officials said on Thursday.
The bulk of the forces will be American, with the Pentagon sending 3,000 troops to Kabul's airport. The troops will come from two marine infantry battalions and will arrive in the next two days, Pentagon spokesman John Kirby said.
US State Department spokesman Ned Price said the US was working to forge an international consensus behind the need for a peace accord.
Faizabad, in the north-eastern province of Badakhshan, fell to the Taliban on Wednesday.
Mr Ghani flew to Mazar-i-Sharif this week to rally old warlords to the defence of the biggest city in the north as Taliban forces closed in.
US President Joe Biden said this week that he did not regret his decision to withdraw and urged Afghan leaders to fight for their homeland.
Washington has spent more than $1 trillion over 20 years and lost thousands of US troops, and continued to provide significant air support, food, equipment and salaries to Afghan forces, he said.
White House Press secretary Jen Psaki said the plan to withdraw troops by August 31 held and reiterated the administration's view that Afghan forces have the US support they need to fight back.
The Afghans “need to determine if they have the political will to fight back and if they have the ability to unite as leaders to fight back,” she said.
But former US national security adviser HR McMaster said the fallout from the withdrawal would be devastating.
Speaking virtually to the Wilson Centre in Washington, Mr McMaster said what comes next may be worse than the bloody civil war that ravaged the country from 1992 to 1996.
“This will be that crisis on steroids,” he said. “Why? You know, in 2001, the population of Kabul was 500,000. Today, it's over 5 million.”
Mr McMaster feared the US withdrawal could amount to a failure to meet the Responsibility to Protect doctrine signed by UN member states in 2005.
“Where are the people in the Biden administration who were the authors of the [Responsibility to Protect] doctrine? Remember the right to protect after we stood idly by in a genocidal campaign in Rwanda?” he asked.
“What are they saying now? Because I would imagine they were in on the decision about the complete withdrawal from Afghanistan.”
The Taliban's advance has raised fears of a return to power of the hard-line militants who surfaced in 1994 from the chaos of civil war.
They controlled most of Afghanistan from 1996 to 2001, when they were ousted by a US-led campaign for harbouring Al Qaeda chief Osama bin Laden.
A new generation of Afghans, who have come of age since 2001, fears the progress made in areas such as women's rights and media freedom will be lost.
Afghan officials have appealed for pressure on Pakistan to stop Taliban reinforcements and supplies flowing over the border. Pakistan denies backing the Taliban.
Pakistani Prime Minister Imran Khan said Taliban leaders told him this year they will not negotiate with the Afghan government as long as Mr Ghani remains president.
Mr Ghani is appealing for help from the regional warlords he spent years sidelining as he tried to project the authority of his central government over wayward provinces.
The Taliban have captured districts bordering Tajikistan, Uzbekistan, Iran, Pakistan and China, heightening regional security concerns.