A search was under way Wednesday for 11 Niger soldiers missing since an ambush by armed men the day before left 17 of their colleagues dead and several injured, security sources said.
A military patrol was ambushed Tuesday afternoon near the village of Tongo Tongo in the western Tillaberi region along the border with Mali, they said.
One of the military vehicles had set off an explosive device.
A source said the "provisional" death toll of 17 may yet rise, and referred to a "terrorist attack".
Several troops were injured and evacuated to the capital Niamey, a different source told.
By Wednesday, "several soldiers were still not responding to calls," said another, adding that "search operations are ongoing."