An ambush by a “group of criminals” killed at least 10 Nigerien soldiers near the country’s border with Burkina Faso this week, Niger’s ruling military junta said.

An intervention unit was sent to the west of the country on Monday to catch criminals stealing cattle in Takzat, a village in western Niger, according to a military statement said broadcast on Wednesday night.

“It was during the operation that a group of criminals ambushed the detachment of the internal security forces which resulted in the loss of 10 of our soldiers,” it said. It did not specify who the criminals were.

The attackers managed to flee, but the military caught and neutralized 15 “terrorists” on Tuesday, the statement added.

Niger, along with its neighbors Burkina Faso and Mali, has for over a decade battled an insurgency fought by jihadi groups, including some allied with al-Qaida and the Islamic State group.

Following military coups in all three nations in recent years, the ruling juntas have expelled French forces and turned to Russia’s mercenary units for security assistance. The three countries vowed to strengthen their cooperation by establishing a new security alliance, the Alliance of Sahel States.

But the security situation in the Sahel, a vast region on the fringes of the Sahara Desert, has significantly worsened since the juntas took power, analysts say, with a record number of attacks and civilians killed both by Islamic militants and government forces.

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Ten soldiers were killed and seven others injured in an attack near Niger’s border with Burkina Faso last December, the army said.

The same month, militants of an Islamic State group affiliate — known as Islamic State Sahel Province — likely shot and killed 21 passengers on a bus in the Arboudji village, near the border with Burkina Faso, according to the U.S.-based Armed Conflict Location and Event Data.