In a post on the IS-affiliated Amaq online channel, the Islamic State West Africa Province (ISWAP) said its fighters "killed a senior officer in the Nigerian army after a successful ambush they set up for a military force...in the north of the country" on Saturday.

The post was accompanied by two pictures, one showing Brigadier General M. Uba sitting on the ground and another sitting in his office before his capture.

If confirmed, Uba would be the highest ranking officer killed since 2021 in the country's long running jihadist war.

The commander of Nigerian army's 25th brigade in the town of Damboa went missing on Friday after an army convoy was ambushed by ISWAP fighters near the town of Wajirko in northeastern Borno state.

On Saturday, the Nigerian army dismissed as "fake narrative" local media reports that Uba had been captured, insisting he had returned to base after the ambush which killed two soldiers and two fighters from a militia helping the army fight jihadists.

A Nigerian intelligence source told AFP late Sunday that Uba had been captured along with 16 soldiers and they were expecting "the worst scenario".

ISWAP "left his mobile phone on long enough for the military to get his coordinates," the intelligence source said.

"They made him make a video call with his friend...and then switched off the phone. Rescue team mobilised to the location but could not find him," added the source.

The army did not respond to an AFP request for comment.

ISWAP, which split from Nigeria's Boko Haram jihadist group in 2016, has focused on attacks on military targets in the northeast, raiding bases, planting mines and laying ambush against troops.

Four years ago, a brigadier general was killed along with three soldiers while repelling an ISWAP attack in Borno, while in October a lieutenant colonel was killed in an ambush in Bama town.

The 16-year jihadist violence has killed more than 40,000 people and displaced around two million in the northeast.