A U.S. official told The Daily Beast on Monday that all six of the NATO troops killed in an attack by a suicide bomber on motorcycle near Afghanistan's Bagram Airfield were Americans. Provincial police said Afghan and Western forces were moving in a convoy when the blast occurred. Three additional NATO troops were injured—it is not yet known what their nationalities are. Taliban officials posted a message on Twitter claiming responsibility for the attack. Secretary of Defense Ash Carter visited the air base north of Kabul just last week.