Fifteen Boko Haram militants were killed Wednesday and 20 others captured, in a confrontation with Nigerien military, a military spokesman said, adding that the country’s soldiers have also destroyed ammunition, cars and motorcycles seized from the militants.

The attack in Niger by its military came the night after Boko Haram members had attacked the village of Yebbi in the Diffa region Tuesday night, killing five residents and burning more than 100 homes, army spokesman Col. Michel Moustapha Ledru said on state TV late Wednesday night.

The Nigerian extremist group began launching cross border attacks this year after international forces, including Niger’s army, began fighting the insurgency. Attacks last week in two villages in Niger left more than 40 people dead.

“We honor the defense and security forces who have proven their professionalism in the response against terrorist elements of Boko Haram,” Ledru said.

Boko Haram’s six-year-old uprising, which began in northeastern Nigeria, is blamed for the deaths of 13,000 people and the displacement of more than 1.5 million.

Boko Haram has stepped up attacks since Nigeria’s new President Muhammadu Buhari announced the military command center will be moved from the capital Abuja to Maiduguri in Borno State, the birthplace of the extremist group.

Nigeria and its neighbors are also preparing to strengthen a multinational army that this year drove Boko Haram out of towns and villages where it had set up a so-called Islamic caliphate.

The U.S. Department of State on Thursday condemned recent attacks within Nigeria, adding that they “serve as a reminder that despite progress on the battlefield, Boko Haram remains capable of deadly and destabilizing acts of terrorism.”

The press statement from spokesman John Kirby said: “We commend the efforts by the Nigerian military, as well as the militaries of Chad, Niger, and Cameroon for the gains they have made fighting Boko Haram”.