One US official says strike was carried out by an unmanned aircraft piloted from outside Afghanistan, and secondary explosions showed the target had been carrying a "substantial amount of explosive material"
Suicide bombers set off two blasts that struck crowds outside the Afghan capital's airport on Thursday, killing dozens of people including 13 US troops
"We're not in a position to attribute it officially just yet but of course it does bear all the hallmarks of the spate of Taliban attacks that we have seen in recent weeks," State Department spokesman Ned Price told reporters.