For more than a decade, violent extremism in Nigeria was largely confined to the country's Northeast where militant Islamist movement Boko Haram and its factions have waged an extended armed rebellion against the state.

Over the past few years, however, the borderlands across Nigeria's North West and North Central regions have become a melting pot for Sahelian and local jihadists.

The area, known as the Kebbi-Kainji-Borgu triangle, straddles the Nigerian states of Kebbi, Sokoto, Niger and part of Kwara in central Nigeria. It stretches across the border into Niger's Dosso region and Benin's Alibori department.

The actors include homegrown jihadist groups such as the Sadiku‑led faction of Boko Haram, as well as Ansaru and the Mahmudawa group whose leaders were arrested last year, alongside criminal gangs known locally as bandits.

Together, these groups are believed to number in the hundreds of thousands, raiding villages and killing or displacing communities across the region.

The Sahelian push south

In what appears to be a new phase of expansion for Sahelian jihadists into coastal West Africa, groups like the al-Qaeda-affiliated Jama'at Nusrat al-Islam wal-Muslimin (JNIM) and Islamic State Sahel Province (ISSP) have established their presence in the area.

The move follows sustained military pressure amid growing rivalry between the groups in the Liptako-Gourma tri-state area where the borders of Burkina Faso, Mali, and Niger meet.

In late October last year, JNIM claimed its first known attack in the country after attacking a military position in Karonji in Kwara state.

Meanwhile, an IS Sahel-affiliated jihadist group has expanded its operations in border communities across Sokoto and Kebbi in northwestern Nigeria.

The group called Lakurawa, which has become a catch-all phrase for Sahelian militants in the area, was the target of the US Christmas bombing in Nigeria.

Lakurawa has expanded across the border into Benin's Alibori department and Niger's Dosso and Tahoua, especially around Dogon Kiria, Bagaroua and the rural commune of Allela. 

The group runs the affairs of local communities, appointing imams, levying taxes, and enforcing extreme religious views on villages.

Why the tri-border corridor?

The borderlands connecting Niger, Benin, and Nigeria form a vast stretch of ungoverned territory and underserved communities. 

There are also extensive forest reserves like the Kainji National Park crisscrossing the region and, in some of these rural communities, state presence is partly or nearly absent as security thins out, making border control limited.

For armed groups, analysts say this area not only allowed them to establish new operational bases and expand their logistical network through access to smuggling and illicit trade routes but also offered new manpower and recruitment opportunities.

Operating on the fringes of the borders provides strategic depth where fighters can stage attacks in one country and retreat into neighboring countries.

For instance, Mahmudawa fighters like other groups have been seen moving between their traditional strongholds in Kwara into Benin's Borgu and Alibori departments such as Kandi, Kalale, and Nikki, as part of efforts to establish that corridor.

How the network interacts

James Barnett, a Lagos-based research fellow with the Hudson Institute, said that relationships between the various jihadist groups, including with criminal gangs, remain complex and overlapping, with some degree of cooperation among them.

There are instances of collaboration between groups like JNIM and the Mahmudawa group and Lakurawa and a faction of Boko Haram along the triangle.

Analysts argue that the Mahmudawa group, for instance, has potential ties and possibly helped facilitate access to local networks for JNIM to expand into the areas and establish bases within the Kainji Lake National Park.

"A lot remains unclear about the extent of cooperation between different armed groups in the Kainji axis, but it seems that they have largely managed to deconflict, which is worrying," Barnett told DW.

Barnett added that infighting among jihadist and armed groups has sometimes limited their expansion, so any modus vivendi along that axis "gives each group a degree of freedom to pursue its own operations, much to the detriment of local security."

He noted that there seems to be "cooperation between at least several of the groups there."

"I don't expect all the groups to rally under a single flag anytime soon, but the dynamics there are very worrying," Barnett added.

Changing security landscape and threatened regional stability

Experts told DW the emerging insurgency corridor could reshape Nigeria's security landscape and further destabilize a region already strained by weak cooperation, hampering intelligence sharing and joint operations.

Situations like this, they said, allow jihadist groups like Lakurawa or IS Sahel to operate across the porous borders with Niger and Benin.

Heni Nsaibia, a researcher at Armed Conflict Location & Event Data (ACLED), a global organization that collects data on conflicts worldwide, believes these gaps need to be closed to prevent the groups from "infiltrating and withdrawing to the other side of the border."

Across multiple fronts, Nigeria faces a fluid security situation.

The many forests in the northwest and part of the central region harbor bandits who take advantage of the rural largely ungoverned spaces.

The country's military is stretched thin because of deployments elsewhere, particularly to quell Boko Haram and its factions in the northeast, separatists in the southeast and farmer-herder crisis in central Nigeria.

Heni said a new insurgency corridor along the Kebbi-Kainji-Borgu triangle would place even greater pressure on already strained resources.

With groups that have gained experience in the Sahel, and trying to replicate this in new theaters where the conditions also are advantageous, Heni believes the baseline is about "providing security to local border communities."

And to achieve this, he says, "there's a need for a certain degree of regional cooperation and border security coordination" while rebuilding trust with local communities.

Edited by: Keith Walker