No group has yet claimed responsibility for the attack.
Five soldiers from Niger and three U.S. Army Special Forces were killed and an unspecified number of others were wounded in an ambush on a joint patrol in southwest Niger on Wednesday night.
A spokesman for the U.S. Africa Command confirmed the attack to Radio France International (RFI) by telephone.
“We can confirm reports that a joint U.S. and Nigerien patrol came under hostile fire in southwest Niger,” the spokesman said.
Namatta Abubacar, an official in the Western African nation's Tillaberi region, told Niger TV that five Nigerien soldiers were among the dead.
A statement issued by U.S. Africa Command said, “A joint U.S. and Nigerien patrol came under hostile fire in southwest Niger."
It added, "U.S. forces are in Niger to provide training and security assistance to the Nigerien armed forces including support for intelligence, surveillance and reconnaissance efforts to target violent extremist organizations in the region. One aspect of that is training, assisting and advising Nigeriens to increase their ability to bring security and stability to their people."
No group has yet claimed responsibility for the attack but the area is largely controlled by insurgents, including members of al-Qaeda in the Islamic Maghreb (AQIM) and Daesh.
African security forces backed by Western troops are stepping up efforts to counter jihadist groups forming part of a growing regional insurgency in the troubled Sahel region, where several groups are roaming.
Presidents of the Sahel countries of the region -- including Mali, Niger, Mauritania, Burkina Faso and Chad -- are working on final modalities to set up a G5 Sahel force to help fight the numerous groups who are active in the region.