U.S. President Joe Biden warned on Saturday that another militant attack was highly likely as U.S. troops began leaving Kabul airport after a two-week scramble by Washington and its allies to evacuate citizens and at-risk Afghans.

As Washington neared the end of its military involvement in the country with the Taliban militants it ousted 20 years ago back in power, the United States said it killed two Islamic State militants planning attacks in Afghanistan after a deadly suicide bombing outside the airport on Thursday.

American officials also warned of a high risk of additional attacks by the group — enemies of both the West and Afghanistan's new Taliban rulers — as U.S. forces wind up their mission before a Tuesday deadline set by Biden.