"Hundreds of Mujahideen of the Islamic Emirate are heading towards the state of Panjshir to control it, after local state officials refused to hand it over peacefully," the group wrote on its Arabic Twitter account.
Since the Taliban took control of the country following a lightning charge into the capital Kabul, thousands of people have made their way to Panjshir, according to a spokesman for anti-Taliban forces.
In Panjshir, Ahmad Massoud, the son of legendary mujahideen commander Ahmad Shah Massoud who was assassinated by Al-Qaeda two days before the September 11, 2001 attacks, has sought to assemble a force of around 9,000 people to counter the terrorists, the spokesman, Ali Maisam Nazary, told AFP.
Pictures taken by AFP during training exercises show dozens of recruits performing fitness routines, and a handful of armoured humvees driving across the valley northeast of Kabul.
Nazary said the group wants to push for a new system of government, but is prepared to fight if needed.
"Government forces came to Panjshir from several Afghan provinces," Massoud told Saudi Arabia's Al-Arabiya broadcaster Sunday.