By Nasir Waqif
NATO special forces are supporting Afghan troops in Kunduz after Taliban insurgents seized the city, fought off a counter-attack and advanced on the airport.
Heavy fighting was under way near the northern city's airport where government forces retreated, highlighting the potent challenge the militants pose after their lightning capture of Kunduz.
The Taliban's occupation, now in its third day, raises troubling questions about the capabilities of Afghan forces as they battle the militants largely on their own after NATO's combat mission ended last December.
The Afghan army was supposed to be bolstered by its own reinforcements for the campaign to retake Kunduz, but attacks on convoys making their way to the city meant that back-up troops were only trickling in.
"The Taliban have laid landmines and booby traps around Kunduz, slowing the movement of convoys of Afghan army reinforcements driving to the city," an Afghan security official said.
NATO said the foreign special forces have reached Kunduz and US forces have conducted three air strikes around the city since Tuesday (local time) to support the Afghan troops.
The forces comprise US, British and German troops, a Western military source told AFP on condition of anonymity, without specifying the number.
The Afghan spy agency said the overnight strikes killed Mawlawi Salam, the Taliban's "shadow governor" for the province, along with his deputy and 15 other fighters.
But the fall of the provincial capital, which sent thousands of panicked residents fleeing, has dealt a major blow to the Afghan military and highlighted the insurgency's potential to expand beyond its rural strongholds.
The Afghan security official said the militants had slowly infiltrated Kunduz during the recent Eid festival, launching a Trojan horse attack that enabled them to capture it within hours.
Pentagon press secretary Peter Cook said the fall of the city on Monday, achieved by a militant force significantly smaller than the army contingent, was "obviously" a setback, but the US believed Afghan authorities would be able to regain control.
Cook added he was "not sure it reflects any new assessment of the Taliban", but many analysts see it as a game-changer for a group which many had believed was fraying.
The Taliban's recent gains in Kunduz and neighbouring provinces highlight a rapidly expanding insurgency as militants infiltrate into the north from their traditional southern strongholds.
Kunduz's fall has also renewed questions about Washington's plan to withdraw most US troops from Afghanistan next year.
Even after years of training and equipment purchases, on which Washington spent a whopping $US65 billion, Afghan police and troops have been unable to rein in the ascendant insurgency.
"Despite their many improvements in recent years, [Afghan forces] remain a work in progress," said Michael Kugelman, Afghanistan expert at the Washington-based Woodrow Wilson International Center for Scholars.
"And given the extent of the Taliban threat, work in progress isn't good enough."
Despite the counter-attack Kunduz remained largely under Taliban control - the first major urban centre in their grip since they were toppled from national power in 2001.
Insurgents showed off seized tanks and armoured cars, chanting "Allahu Akbar" (God is great) and promising to enforce Islamic sharia law, a Taliban video showed.