A suicide bombing at a U.S. military base in Afghanistan Saturday morning killed four Americans: two service members and two contractors.
The explosion occurred at about 5:30 a.m. local time at Bagram Airfield, the largest U.S. military base in Afghanistan, according to a press release from Resolute Support, the NATO mission in Afghanistan.
Defense Secretary Ash Carter said that in addition to the four Americans killed, 16 U.S. service members and one Polish soldier were also injured in the attack.
“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. Force protection is always a top priority for us in Afghanistan, and we will investigate this tragedy to determine any steps we can take to improve it,” Carter said in a statement.
NATO Secretary General Jens Stoltenberg also mourned those lost in the attack on Twitter.
“My thoughts go to the loved ones of those killed at #Bagram Airfield & the wounded. #NATO stands w/ #Afghanistan in the fight against terror,” he wrote.
The identities of the troops and contractors killed have not yet been released pending notification of their next of kin.
