Four American troops were killed in an attack at the Bagram air base in Afghanistan.
An official from the Pentagon said the soldiers were killed either in a rocket or mortar shell attack at the Bagram air base, the largest military base for US troops, near the Afghan capital, Kabul.
The attack came after the US announced that it would start direct talks with the Taliban in Qatar.
NATO on Tuesday also handed over responsibility for security to the Afghan security forces.
Officials have yet to make a statement yet.
