Three US service members were killed Tuesday by an improvised explosive device near the city of Ghazni, Afghanistan, the US military announced.
Three US service members and an American contractor were also wounded in the blast, the military said.
The names of those killed were not immediately disclosed pending the notification of next of kin.
No other details were immediately released. But the attack comes as the Taliban have strengthened their grip over the country in recent years.
A recent report released by the US government's own ombudsman of the war found that the Afghan government now controls 56% of the districts in the country, down from 72% in November 2015. Insurgent influence or control has risen to 12.5% of districts from just 7%, and approximately a third of Afghanistan is a "contested" area.