NIAMEY (Reuters) - Niger will launch a new military offensive against Islamist militants after their latest attack on an army base killed at least 25 soldiers, the defense minister said on Friday.

Thursday’s attack near the Malian border followed a raid by Islamic State insurgents on a military outpost last month that killed 71 soldiers. That was the deadliest strike against Nigerien forces for years and underscored deteriorating security conditions across West Africa’s Sahel region.

Despite the presence of French and American troops, attacks in Niger have risen fourfold over the past year, killing nearly 400 people, according to data from the Armed Conflict Location & Event Data Project, a non-profit research organization.

“The strategy has to change,” Defense Minister Issoufou Katambe told Reuters. “We are not going to stay on the defensive. We will go on the offensive.”

Katambe did not provide details. Repeated Nigerien offensives against the militants, often backed by soldiers from France’s 4,500-strong Sahel task force, have failed to curb violence near the western border with Mali.

Military campaigns by armies in the Sahel, a semi-arid swathe of land beneath the Sahara, have also been marred by human rights abuses, which analysts say have pushed some civilians into the arms of the jihadists.

In addition to the Islamist attacks, countries in the region, especially Mali and Burkina Faso, have struggled to cope with deadly ethnic reprisals between rival farming and herding communities.

Mohamed Ibn Chambas, the U.N. secretary-general’s representative in West Africa, told the Security Council this week that deaths from militant attacks in Niger, Mali and Burkina increased from about 770 in 2016 to over 4,000 in 2019.

“The region has experienced a devastating surge in terrorist attacks against civilian and military targets,” Chambas said.

The regional G5 Sahel force, made up of soldiers from Mali, Mauritania, Niger, Burkina Faso and Chad, was launched in 2016 but has struggled to coordinate against armed groups linked to Islamic State and al Qaeda who frequently ghost over long, unpoliced borders.

No one has claimed responsibility for Thursday’s attack in Chinagodrar, which is about 130 miles (210 km) north of the capital Niamey.

The assailants approached the military post on motorcycles and other vehicles, the government said. Sixty-three assailants were killed in the ensuing firefight, it said.