Islamic State insurgents have killed seven leaders of the Tuareg ethnic group in southwestern Niger in less than three months, as part of a strategy to create a political void in the region, officials said on Tuesday, July 16.

Three traditional Tuareg chiefs and four senior Tuareg officials have been killed since late April by Islamic State in the Greater Sahara in the volatile region of Niger on the Mali border, they said.

Arrisal Amdagh, a Tuareg chief in the rural district of Inates, was shot dead at his home in late April, and his son Almoubacher Ag Alamjadi, who succeeded him, was killed on Monday, a Niger security source said.

Their deaths were confirmed to AFP by Defence Minister Kalla Moutari on Tuesday.

Four senior members of the tribe were killed by a roadside bomb as they were heading to the father’s funeral, their relatives said last month.

In a separate incident in June, a traditional Tuareg leader in Bankilare district was kidnapped and killed, a local source said.

“The ISGS strategy is to kill traditional chiefs in the border areas,” a security source told AFP. “It’s a way of voiding the area of an effective state presence, enabling you to move in and impose your law.”

One of the world’s poorest countries, Niger lies in the heart of the fragile Sahel region.

Niger faces insurgency on two fronts: the southeastern Diffa region near Lake Chad is increasingly frequently hit by Nigeria-based Islamic State West Africa Province insurgents, while militants based in Mali, including al-Qaeda-affiliated fighters, are active in the west of the country and the wider Sahel.

Attacks carried out by ISIS-affiliated militants in the Sahel have previously been attributed to Islamic State in the Greater Sahara but since May, Islamic State has attributed insurgent activities in the Mali-Burkina Faso-Niger tri-border area to ISWAP, rather than ISGS.

On July 1, 18 Nigerien soldiers were killed when insurgents attacked an army camp near Inates, according to the defense ministry. Islamic State later said fighters from its West Africa Province affiliate carried out the raid.

In June, 18 Islamic State militants were killed in during the joint Operation Aconit by French and Nigerien troops near Tongo Tongo to the east. The 13-day Operation Aconit also involved a joint Mali-France commando operation that killed 20 ‘terrorists’ in Mali’s Menaka area.

The recent unrest in the Sahel began in Mali in 2012 with a Tuareg separatist uprising that was exploited by Islamist extremists linked to al-Qaeda who took key cities in the desert north.

France began its Operation Serval military intervention in its former colony early the next year, driving jihadists from the towns, but the militant groups morphed into more nimble formations operating in rural areas, and the insurgency has gradually spread to central and southern regions of Mali, and across the borders into neighboring Burkina Faso and Niger.

The French mission evolved in August 2014 into the current 4,500-strong Operation Barkhane, which has a mandate for counter-terrorism operations across the Sahel, and other nations including the United Kingdom and Estonia have deployed troops and aircraft to the mission. Troops deployed to Barkhane work alongside other international operations, including the roughly 14,000-strong U.N. MINUSMA mission in Mali, and the regional G5 Sahel joint counter-terrorism force that aims to train and deploy up to 5,000 personnel from the five members.

Last week, the European Union said is to give €138 million ($155 million) more to support the G5 Sahel Joint Force, comprised of Burkina Faso, Chad, Mali, Mauritania and Niger.

On July 5, Niger’s President Mahamadou Issoufou again called for called for sustainable U.N. funding for the force under Chapter VII of the U.N. Charter, noting that “Niger will use its position as a non-permanent member of the Security Council, from 2020, to promote this position.”

Many Security Council members have called called for “predictable” U.N. funding for the Joint Force, but the United States has opposed this, opting instead for bilateral assistance.

Niger hosts an estimated 800 U.S. troops, the largest American deployment in Africa. The U.S. is building a large and controversial drone base known as Niger Base 201 in the northern city of Agadez, and Niger recently gave the Americans permission to arm their drones.

Issoufou also proposed “an international coalition of countries to fight terrorism in the Sahel, just as there was a coalition against Daesh in the Middle East,” if Chapter VII funding cannot be agreed.

With reporting from AFP