"The Department of Defense confirmed the deaths of 10 CH-53E crewmembers as a result of the crash that occurred off the coast of northern Djibouti Friday," the Combined Joint Task Force-Horn of Africa said in a statement.
“Our deepest sympathy and heartfelt prayers go out to the family members, friends, loved ones and co-workers of our fallen brothers- and sisters-in-arms," task force commander Major General Timothy Ghormley said. "We mourn their loss and honor their memory," he said.
According to the statement eight of those killed were US Marines and two were Air Force airmen. Two others survived the crash and on Saturday were said to be in a stable condition but since no further update has been given.
The helicopters crashed during a two-hour training mission part of counter-terrorism exercises at the task force base in Djibouti. Both were part of a squadron based at the Marine Corps' New River Air Station in the southern US state of North Carolina.
Officials have not commented on the cause of the crash but did say an investigation is underway. The military said the weather at the time the choppers went down was partly cloudy with light to variable winds and "unlimited visibility."
Djibouti, a former French colony is home to France's largest overseas military base and the only US military base in Africa.
It hosts some 3,000 French, 1,700 US and several hundred Dutch, German and Spanish troops participating in a US-led anti-terrorism operation known as "Enduring Freedom", launched after the September 11, 2001 attacks in the United States.