An ambush by a “terrorist group” killed 21 Nigerien soldiers near the country’s border with Burkina Faso on Tuesday, Niger’s ruling military junta said in a statement read on national television. The statement Tuesday evening did not specify which group was behind the attack. Niger is struggling with a deadly security crisis involving several armed groups.

Last week, the rebel Patriotic Liberation Front attacked a China-backed pipeline and threatened more attacks if the $400 million deal with China isn’t canceled.  The group, led by Salah Mahmoud, a former rebel leader, took up arms after the junta staged a coup last year.