President Ashraf Ghani has repeatedly raised fears that ISIS -- notorious for their brutal reign of terror in Syria and Iraq -- are making steady inroads into Afghanistan, which is already in the grip of a fierce Taliban insurgency.
But the governor of Kunduz, the scene of intense fighting for two weeks that has displaced thousands, has gone further by claiming that the two groups are joining forces in the northern Afghan province.
ISIS fighters are "supporting the Taliban, training the Taliban, trying to build the capacity of the Taliban for a bigger fight", provincial governor Mohammed Omar Safi told the BBC.
Local observers have viewed claims of ISIS's rise in Afghanistan with caution.
The Middle Eastern group has never formally acknowledged a presence in Afghanistan and most self-styled ISIS insurgents in the country are believed to be Taliban turncoats rebranding themselves to appear a more lethal force.
The two groups, which espouse different ideological strains of Sunni Islam, are believed to be arrayed against each other in Afghanistan's restive south, with clashes frequently reported.
But the governor insisted that the fight is different in the once-tranquil north, which has recently seen a huge influx of foreign fighters from countries such as Chechnya, Pakistan and Tajikistan.
"In the worst affected Imam Sahib district, (ISIS) fighters are training and supporting local Taliban fighters to raise their capacity... in their fight against the Afghan government," the governor's spokesman Abdul Wadood Wahidi told AFP.
Last month hundreds of militants came within six kilometres (3.7 miles) of Kunduz city just hours after the Taliban launched their annual spring offensive, in the most serious threat to any provincial capital since the US-led 2001 invasion of Afghanistan.
The insurgents have since been pushed back after Afghan reinforcements were brought in from other frontlines, but the fighting still continues to rage on the fringes of the city.
Tens of thousands of people have been displaced due to the clashes, with aid agencies warning of dire living conditions for those who have fled their homes and moved to the city centre.
"Around 14,000 families have been displaced in two weeks of ongoing fighting in Kunduz," Ghulam Sakhi, an administrator in the Kunduz refugees department, told AFP.
"Our teams have surveyed 600 families and have distributed food items and blankets, mattresses and kitchen kits."
Afghan government forces are preparing for a fresh offensive to flush out insurgents from the outlying areas of the city, officials said.
President Ghani has warned that ISIS poses a serious threat to regional security, warning that the group was more lethal than Al-Qaeda.
"With all apologies to Microsoft, if Al-Qaeda was Windows One, Daesh is Windows Five," he told reporters recently.
But some local observers accuse him of grabbing world attention by playing up the ISIS threat in the face of dwindling foreign aid and as international troops depart.
The Kunduz governor's claim reflected his desire to attract the attention of the central government to the dire security situation in his province, said Kate Clark, of the Afghan Analysts Network.
"Just because they are foreign fighters does not mean they are Daesh," she told AFP.
"I'm sceptical because I can't see any reason why the Taliban would want to fight alongside Daesh. We need to see more evidence to support this claim."