Story highlights There's no shortage of battle-hardened militants in Afghanistan, writes Nick Paton-Walsh

Concerns are growing about how ISIS may expand into the country

A senior U.S. official fears disaffected Taliban might be attracted to the group

Kabul, Afghanistan (CNN) It is a strangely formal, yet troubling scene. A room in a far flung corner of Afghanistan where a serious lecture is happening, to an audience that seems part ideological, part curious; some are just impoverished, hoping for a quick job.

At the front of this room stands an Afghan freshly back from fighting in Syria, and intent on recruiting other Afghans to fight alongside him for ISIS.

"Brothers, I am here to tell you", the recruiter begins, "about the mujahideen in Syria."

All faces are hidden in the footage, yet the motivations are clear. This seems to be part of ISIS's first moves into Afghanistan, a bid to bolster their ranks for the fight in Iraq and Syria by vacuuming up disgruntled former Taliban fighters -- or even just students looking for a cause.

But it's a troubling move nonetheless. There's no shortage of battle-hardened militants here. And as NATO leaves, the Taliban looks strong if a little fractured -- and the possibility of peace talks ahead with the Afghan government could alienate some of the group's more radical elements.

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