U.S. troops helping to evacuate Afghans desperate to flee Taliban rule braced for more attacks on Friday after the Islamic State group struck the crowded gates of Kabul airport, killing scores of civilians and at least 13 U.S. troops.

Kabul health officials were quoted as saying 60 civilians were killed in the attack on Thursday. Video shot by Afghan journalists showed dozens of bodies strewn around a canal on the edge of the airport. At least two blasts and gunfire rocked the area, witnesses said.

IS said one of its suicide bombers targeted "translators and collaborators with the American army." U.S. officials also blamed the group and vowed retribution.