The Islamic State West Africa Province (ISWAP) had claimed on Monday its fighters ambushed and killed a senior officer in the northern Chad region days earlier, in a post alongside a picture of Brigadier General Musa Uba.

The jihadist group said the general was wounded in the leg and was attempting to flee when he was abducted.

"I am depressed with the tragic death of our soldiers and officers on active duty. May God comfort the families of Brigadier General Musa Uba and other fallen heroes," Tinubu said in a statement.

The Nigerian army initially dismissed reports that Uba had been captured in the ambush.

But a Nigerian intelligence source told AFP on Sunday evening that Uba had been taken by ISWAP fighters and that the "worst-case scenario" was feared.

According to the army and a United Nations report, two soldiers and two members of a self-defence group were killed in the attack.

ISWAP broke away from the Boko Haram jihadist group in 2016 and is focused on attacking the Nigerian army.

The jihadist insurgency has killed more than 40,000 people and displaced nearly two million in northeastern Nigeria since 2009, and has spread to neighbouring Niger, Chad and Cameroon.

Uba is the second senior officer killed in a jihadist ambush in four years, after General Dzarma Zirkusu, who died in November 2021.