WASHINGTON — Two members of the Navy’s elite SEAL Team 6 and two Marine Corps Special Operations troops have been charged in the strangling of an Army Green Beret last year in Mali, a highly unusual fratricidal killing that cast a spotlight on little-known military missions in Africa.

The two Navy commandos and the two Marine Raiders face charges that include murder, conspiracy, obstruction of justice, burglary, involuntary manslaughter and lying to investigators in the June 2017 death of the Green Beret, Staff Sgt. Logan J. Melgar, 34, a veteran of two tours in Afghanistan.

The charges against the four commandos, announced by the Navy on Thursday, were brought a day earlier by Rear Adm. Charles W. Rock, the commander of Navy Region Mid-Atlantic in Norfolk, Va. Admiral Rock was assigned this month by the Navy secretary, Richard V. Spencer, to oversee the case. A preliminary hearing in military court in Norfolk is scheduled for Dec. 10 to determine whether the four men face court-martial or some other punishment.

Sergeant Melgar’s killing was one of several violent deaths last year under mysterious circumstances for American troops on little-understood missions in West Africa. Four American soldiers were killed in an ambush in October 2017 in neighboring Niger while conducting what was initially described as a reconnaissance patrol but was later revealed to be part of a much more dangerous counterterrorism mission against Islamic militants in the area.