Who are the group that attacked Kabul airport?

IS-K, a local branch of Islamic State, claimed responsibility for a deadly attack outside Kabul’s airport in Afghanistan on Thursday, which killed up to 170 people.

The bomb blast came hours after Western governments had warned their citizens to stay away from the airport because of an imminent threat from the militant group.

But who exactly are IS-K (also known as ISIS-K), and what threat do they pose to Afghanistan?

Video produced by Cordelia Hemming.