Three U.S. service members and a civilian contractor were killed by an improvised explosive device on Monday near Bagram Air Base, Afghanistan, officials have announced.

Another three U.S. service members were wounded by the blast and are being treated for their injuries, according to a statement from Operation Resolute Support.

Details about what happened where not immediately available. The names of the fallen troops are being withheld pending next of kin notification.

Four other U.S. soldiers have been killed in Afghanistan so far this year: Special Forces Sgt. 1st Class Will D. Lindsay, Spc. Joseph P. Collette, Special Forces Sgt. 1st Class Joshua Z. Beale, and Army Ranger Sgt. Cameron A. Meddock.

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