US official: IS group believed to be behind Kabul attack

A US official says the complex attack outside Kabul airport is "definitely believed" to have been carried out by the Islamic State group.

The official says members of the US military were wounded in Thursday's attack, which involved two suicide bombers and gunmen.

Read more: 2 suicide attacks outside Kabul airport; at least 13 dead

The official spoke on condition of anonymity to discuss ongoing operations. The Islamic State group is more radical than the Taliban and has carried out a wave of attacks targeting civilians.

The official says evacuation flights have continued to take off from Kabul airport in the waning days of an airlift to help people flee the Taliban takeover of Afghanistan.