Follow the latest updates on Afghanistan here.
Hours before a series of bombings rocked Kabul airport, the US and other western governments warned of the threat of attacks.
With the Taliban upholding an agreement not to attack evacuation operations, the main risk was from ISIS.
Dozens of people were killed in the attacks, including a number of US soldiers, and scores were wounded.
Though the US and the Taliban have reached a political deal to end America's longest war, ISIS has continued to attack both sides.
“The ISIS attack on the airport, while anticipated by US and western intelligence, was a political signal by the ISIS-Khorasan branch that it — unlike the Taliban — will continue attacking American and western targets,” said James Jeffrey, former US special envoy to the global coalition against ISIS and director of the Middle East Programme at the Wilson Centre in Washington.
“This is a fundamental challenge to Taliban control and underscores the continued threat from Afghanistan after the American withdrawal.”
Who are ISIS-K?
Named after a historical term for the region, Islamic State-Khorasan (ISIS-K) first appeared in eastern Afghanistan in late 2014 and quickly established a reputation for brutality, even in a country where extreme violence was regularly witnessed.
An offshoot of the branch of the group operating in Iraq and the Levant, the group challenged the Taliban for control over vital areas on the border with Pakistan, which have been associated with drug smuggling.
Through a series of attacks on civilians and military forces, it established itself as an even more extreme version of the Taliban.
After its formation, the group launched hundreds of attacks in Afghanistan and Pakistan between 2015 and 2017, and it is believed to be responsible for at least 250 attacks on Afghan, Pakistani and US forces.
How big are ISIS-K?
The UN estimates that the group is made up of anywhere between 500 to 1,200 fighters, although experts believe that number could rise to 10,000 over the next few years.
It is also believed that the group was formed by elements of the Pakistani Taliban that fled into Afghanistan following a government crackdown.
Days after the Taliban took over Afghanistan, ISIS threatened to attack Kabul airport as Afghans and foreigners attempted to flee the country. Shortly after that threat was made, the airport attack occurred.
Despite its name, the connection between ISIS-K and ISIS in the Middle East remains unclear.
Intelligence officials believe, however, that ISIS-K capitalised on the situation in Afghanistan to bolster recruitment to its ranks.
Is there a connection between ISIS-K and the Taliban?
Competition between the Taliban and ISIS-K is not merely over territory but also over their divergent ideology — ISIS supporters have claimed that the Taliban are not leading a real “Islamic resistance” movement but are merely puppets of the West.
The Taliban claim to have taken over large areas of the country from ISIS-K and wiped out its members in Afghanistan's north-western territory of Jowzjan.
Though unconfirmed, reports say that the Taliban have executed at least one senior ISIS-K official since their takeover of the country.