A heavy explosion rocked Darul-Amman area of capital Kabul early Saturday.
The incident took place after a suicide bomber detonated his explosives near a foreign troops convoy on Darul Amman highway, around 11:30 am.
The bombing was the single deadliest assault on Americans in the capital since the war began, military officials said, and follows brazen Taliban attacks on the American Embassy and NATO headquarters in the city last month.
A van laden with explosives swerved into a US military armored bus Saturday, killing 13 Americans and at least four Afghans in the Afghan capital. Foreign and Afghan forces arrive at the site of a suicide attack in Kabul.