KABUL (AFP) - Taliban fighters advanced deep into the last holdout province of Panjshir on Sunday (Sept 5), as the top US general warned Afghanistan faces a wider civil war that would offer fertile ground for a resurgence of terrorism.
Following their lightning fast rout of Afghanistan's army last month - and celebrations when the last US troops flew out after 20 years of war on Monday - the Taliban are seeking to crush resistance forces defending the mountainous Panjshir Valley.
The Taliban, who rolled into Kabul three weeks ago at a speed that analysts say likely surprised even the hardline Islamists themselves, are yet to finalise their new regime.
But US General Mark Milley questioned whether they can consolidate power as they seek to shift from a guerrilla force to government.
"I think there's at least a very good probability of a broader civil war," said Gen Milley, chairman of the Joint Chiefs of Staff, in a bleak assessment.
"That will then in turn lead to conditions that could, in fact, lead to a reconstitution of Al-Qaeda or a growth of ISIS (Islamic State in Iraq and Syria)," he told Fox News on Saturday.
Afghanistan's new rulers have pledged to be more accommodating than during their first stint in power, which also came after years of conflict - first the Soviet invasion of 1979, and then a bloody civil war.
They have promised a more "inclusive" government that represents Afghanistan's complex ethnic makeup - though women are unlikely to be included at the top levels.
But few in Panjshir, a rugged valley north of Kabul which held out for nearly a decade against the Soviet Union's occupation and also the Taliban's first rule from 1996-2001, seem to trust their promises.
Taliban official Bilal Karimi on Sunday reported heavy clashes in Panjshir, and while resistance fighters insist they have the Islamists at bay, analysts warned they are struggling.
Italian aid agency Emergency, which runs a hospital in Panjshir, said Taliban forces had reached the village of Anabah, where they run a surgical centre.
"Many people have fled from local villages in recent days," Emergency said in a statement on Saturday, adding it was continuing to provide medical services.
"There has so far been no interference with Emergency's activities," it said.
"We have received a small number of wounded people at the Anabah Surgical Centre."
Anabah lies some 25km north inside the 115km-long valley, but unconfirmed reports suggested the Taliban had seized other areas too.
Bill Roggio, managing editor of the US-based Long War Journal, said on Sunday that there was still a "fog of war" with unconfirmed reports the Taliban had captured multiple districts - but that "it looks bad".
Both sides claim to have inflicted heavy losses on each other.
"The Taliban army has been hardened with 20 years of war, and make no mistake, the Taliban trained an army," Roggio tweeted on Sunday, adding that "the odds were long" for the Panjshir resistance.
"The Taliban army was injected with a massive amount of weapons and munitions after the US withdrawal and collapse of the ANA (Afghan National Army)," he added.
Fighters in Panjshir held out for a decade against the Soviet military and also the Taliban's first regime from 1996-2001.
Ali Maisam Nazary - who is not in Panjshir but remains a spokesman for the resistance - boasted on Sunday that the resistance "will never fail".
But former vice-president Amrullah Saleh, who is holed out in Panjshir alongside Ahmad Massoud - the son of legendary anti-Taliban commander Ahmad Shah Massoud - warned of a grim situation.
Saleh in a statement spoke of a "large-scale humanitarian crisis", with thousands "displaced by the Taliban onslaught".
Pro-Taliban social media have boasted of capturing swathes of the valley, but Nick Waters from the investigative website Bellingcat said the posts did not include verifiable photographs to back up the claims.
"It will be quite easy to verify a video showing Taliban within the Panjshir valley," Waters said.
The Panjshir Valley, surrounded by jagged snow-capped peaks, offers a natural defensive advantage, with fighters melting away in the face of advancing forces, then launching ambushes firing from the high tops down into the valley.
US Secretary of State Antony Blinken is due on Monday in Qatar, a key player in the Afghan saga and the location of the Taliban's political office, though he is not expected to meet with the militants.
He will then travel to Germany to lead a virtual 20-nation ministerial meeting on Afghanistan alongside German Foreign Minister Heiko Maas.
United Nations Secretary-General Antonio Guterres is also set to convene a high-level meeting on Afghanistan in Geneva on September 13, to focus on humanitarian assistance for the country.