CAIRO (AP) — Forces loyal to a powerful Libyan commander said two military planes crashed on Sunday in over a village in eastern Libya, killing at least two officers.

The self-styled Libyan Arab Armed Forces, led by Gen. Khalifa Hifter, said the helicopters collided in the air over the village of Msus, 130 kilometers (about 81 miles) southeast of the city of Benghazi.

A two-officer crew, including Brig. Gen. Bouzied al-Barrasi, was killed in the crash, while the second helicopter crew survived, the LAAF said in a brief statement. The statement did not give the cause of crash and said the helicopters were on a military mission.

Mohammad Younes Menfi, head of Libya’s Presidential Council, mourned the two officers.

Hifter’s forces control eastern and most of southern Libya. The crash came as they have been battling Chadian fighters in Libya’s southern areas on the border with Chad.

The clashes erupted last week and could further destabilize the wider Sahel region, after Chadian President Idriss Deby Itno was killed in April in battels between his government and Chadian rebels.