Troops in northern Cameroon set out Friday for a fresh push against Boko Haram militants, a week after the terror group carried out its deadliest attack in Niger in more than a year.

The militants raided a military post in Bosso, Niger, killing at least 26 soldiers. Niger’s government said 55 insurgents were also killed. The U.N. refugee agency said about 50,000 residents had fled.

General Jacob Kodji, one of Cameroon's top commanders in the north, said troops from Niger and Chad would attack Boko Haram strongholds in Niger, while his men would organize raids to stop the terrorists from getting reinforcements from or escaping to hideouts around the Lake Chad Basin and the Sambisa Forest in Nigeria.

Kodji said the area of operations would span more than 400 kilometers. The operations will be dangerous, he said, because the insurgents are increasingly using land mines and holding civilians hostage as human shields.

Colonel Didier Badjeck, Cameroon’s military spokesman, accused Boko Haram fighters of harassing the population along the country’s border with Nigeria, saying fighters had been stealing food and killing residents.

Badjeck said Boko Haram had been staging attacks daily for three weeks. After an attack on one of its positions, Cameroon’s military struck back against the Islamic militant group Friday, he said.