Four Americans are dead after a man detonated a "suicide vest" early Saturday morning at Bagram Airfield, the largest U.S. military base in Afghanistan, a senior U.S. military official confirmed to NBC News.
Two U.S. service members and two American contractors were killed in the attack, Defense Secretary Ash Carter said in a statement.
Aside from the victims who were killed, an estimated 14 others were injured in the attack, which occurred around 5:30 a.m. local time, as people were gathering for a post-Veterans Day event.
"I want to express my sincere condolences to the families of the fallen, and I want to reassure the loved ones of those injured that they are getting the best possible care," Carter said.
There was no immediate word on the identities of the victims.