Islamic State said it had killed 20 Nigerian soldiers in an attack on Wednesday in the country’s northeastern Borno state.
The claim of responsibility was translated into English and published on the SITE Intelligence website.
Islamic State in West Africa (ISWA), which split from Nigerian Islamist group Boko Haram in 2016, has carried out a number of attacks in the northeast over the last few months.
Reuters had earlier reported that militants on Wednesday took a Nigerian army base at the village of Kareto in northeastern Borno state, some 130 kilometres from state capital Maiduguri, the security sources said.
No other details about possible further casualties were available.
Nigerian army spokespeople did not immediately respond to requests for comment.
The latest development is at odds with the Nigerian military’s public statements as recently as Monday that their campaigns against Boko Haram and Islamic State’s West African branch are making “major breakthroughs”, statements that frequently describe the insurgents as “remnants”.
It was not immediately clear whether the attackers were affiliated with Boko Haram or Islamic State.
The insurgents were said to have overrun troops from the Nigeria Army’s 158th Battalion stationed at Kareto, killing at least their commanding officer and causing the remaining soldiers to flee, one security source said.