Who are Isis-K, and what is their relationship with the Taliban?

Coordinated suicide bomb blasts at Kabul airport on Thursday have left at least 170 dead and many more injured.

Isis-K has claimed responsibility for the attack, which targeted US troops and Afghans attempting to secure the last remaining places on military evacuation flights out of the country.

On Friday, the US said it killed a "planner" for the group in an air strike in Afghanistan.

The threat of further attacks around Kabul Airport will increase as Western troops get closer to leaving the country, Defence Secretary Ben Wallace said on Friday, with Isis-K hoping to show it drove foreign troops from Afghanistan.

"The threat is obviously going to grow the closer we get to leaving," he told Sky News. "The narrative is always going to be, as we leave, certain groups such as ISIS will want to stake a claim that they have driven out the US or the UK." 

On Thursday night, President Joe Biden pledged to "hunt down" the attackers and ordered his military to plan strikes.

He said: "Know this: we will not forgive, we will not forget. We will hunt you down and make you pay." 

Here we look at how Isis-K came to exist and why it poses such a threat to US forces in Afghanistan.