CNN  — 

In the space of just a few years, an ISIS affiliate in Afghanistan has seized on the country’s instability to become one of the region’s most feared terror groups.

ISIS-K has claimed responsibility for the deadly bombing attack outside Kabul airport on Thursday, which targeted a frantic Western evacuation operation and killed 13 US troops and more than 90 Afghans. The group provided no evidence to support the claim but US officials have said it was likely behind the atrocity.

It was ISIS-K’s most globally consequential action to date and drew a promise of retribution from US President Joe Biden.

But the group, known in full as ISIS-Khorasan, has been responsible for thousands of deaths since its 2015 formation.

Its members operate in central Asia, and the group’s name comes from its terminology for the area that includes Afghanistan and Pakistan.

In 2018 it was ranked the world’s fourth deadliest terror group, claiming more than 1,000 lives, mostly in Afghanistan, according to the Institute for Economics and Peace, which monitors global terrorism annually.

Since then the group’s growth has been limited and its militants have fought the Taliban. But they have capitalized on uncertainty in Afghanistan in recent months to launch brutal attacks, and the impending withdrawal of troops by the United States threatens to give them a window in which to regain strength.

The Kabul attack claimed dozens of lives, including 13 US troops and more than 60 Afghans.