Jihadists from rival Al-Qaeda and Islamic State factions in the Sahel have clashed recently on an unprecedented scale in the borderlands spanning Burkina Faso, Mali and Niger, with claims of hundreds of fighters killed.
The two extremist coalitions, which covet influence over the same areas and control of the same routes and local populations, have repeatedly clashed since 2019.
The rivalry also drives their constant expansion in the Sahel, which the ruling juntas in Ouagadougou, Bamako and Niamey have found difficult to contain.
The clashes are "the most intense direct confrontation globally" between an Al-Qaeda branch and an IS-linked group, a report by UN experts submitted to the Security Council in early August said.
A semi-arid belt of land that stretches from the Atlantic Ocean along the southern rim of the Sahara desert to the Red Sea, Africa's Sahel has become the ground zero of global jihadism.
Extremists have steadily expanded beyond the rural areas where they first took root, killing thousands, roiling governments and sowing terror.
Since September, fighting between Islamic State - Sahel Province (ISSP) and the Al-Qaeda-linked Group for the Support of Islam and Muslims (JNIM) has escalated to unprecedented levels.
On Monday, the ISSP said it had killed more than 400 JNIM fighters, including "several leaders", in clashes four days earlier in the Burkinabe province of Oudalan on the Mali and Niger borders.
"If the claimed death toll is confirmed, then it will be the deadliest single battle recorded between the two groups," Heni Nsaibia, an analyst at conflict monitor ACLED, said.
The toll has yet to be independently confirmed.
But if so, it would surpass the more than 200 deaths claimed by the ISSP in the same area in early September.
2,200 deaths since 2019
Between 2019 and last month, the two jihadist groups fought more than 320 battles, resulting in about 2,200 deaths, Nsaibia said.
The latest clashes between fighters from JNIM and IS erupted on October 9 in the tri-border area, according to Wamaps, a collective of west African journalists.
The rivals are fighting over "the same potential living space and the same recruitment pools" in a "race for control of the borders between the three countries", Wassim Nasr, an expert on jihadist groups and an associate researcher at The Soufan Center, said in a recent study.
Long confined to Mali and Burkina Faso, the fighting has in recent months spread to western Niger and even northwestern Nigeria, Nsaibia said.
From its Malian stronghold in Menaka, the ISSP has extended its influence into the Nigerien regions of Tahoua, Dosso and Maradi, up to the Nigerian border, Nasr said in the study.
This facilitates the transfer of fighters, equipment and expertise with ISWAP, the IS branch active in the Lake Chad basin, he added.
Competing visions
Behind the violence lies competing visions of jihad.
While JNIM carries out abuses against civilians, it focuses on developing local roots, building alliances with communities and concentrating attacks on state forces and foreign troops.
The IS group adopts a more hardline, transnational approach and does not shy away from targeting civilians who refuse to kowtow to its authority, Sahel specialist Hasret Kargin said.
Such "enduring ideological and strategic tensions" between the two groups are seen in reported defections — albeit limited in number — from JNIM to ISSP, the UN experts said in their report.
In July, JNIM claimed it had killed one of its commanders, who had defected to join IS.
However, despite the heavy losses the IS claims to have inflicted, JNIM remains the leading terror threat in the Sahel, the UN expert report said.
It estimated that its forces number between 7,000 and 8,000 fighters, compared with 2,000 members of IS.
"There is significant information indicating that JNIM has shifted substantial reinforcements to the area from other regions," Kargin said.
Given its numbers across the Sahel and its strength compared to the Islamic State's Sahel branch, Kargin said he predicted that JNIM would launch "fierce counterattacks in the coming days".