ABUJA, Nigeria (AP) — Militants with the Islamic State group attacked a village overnight in northeastern Nigeria, killing at least 29 people, authorities said Monday. It was the latest violence in Africa’s most populous country that has long been battling a complex security crisis.

The attack took place late on Sunday in Guyaku, a village in the Gombi local government area in the country’s Adamawa state, according to the state governor.

The Islamic State group claimed responsibility for the attack in a message on the Telegram messaging app.

Adamawa State Governor Ahmadu Umaru Fintiri denounced the attack as tragic and unacceptable during a visit to the village on Monday.

Nigeria is facing myriad security challenges, especially in the north, where an insurgency has simmered for more than two decades. In February, the United States sent troops to the West African nation to help advise its military on the fight against insecurity.

There are two major IS-backed militant groups in Nigeria but it wasn’t immediately clear which one was behind the attack in Guyaki.

The Islamic State West Africa Province, or ISWAP, is known to be operating in the northeast, including in Adamawa state, while another IS-linked group known locally as Lakurawa often attacks villages further away in the northcentral states of Sokoto and Kebbi.

The Guyaki attack occurred on the same day that gunmen raided an orphanage in north-central Nigeria and abducted 23 pupils. Fifteen were later rescued and the government said “intensive operations” were underway to “secure the safe return of the remaining eight victims and apprehend the perpetrators.”

Students’ kidnappings have come to define the insecurity in Nigeria, where analysts say armed gangs see schools and students as “strategic” targets to draw attention.

The attack took place in an “isolated area” of Lokoja, capital of Kogi State, according to a statement by the state’s commissioner, Kingsley Femi Fanwo. The facility, Dahallukitab Group of Schools, was operating illegally, he said.

No group immediately claimed responsibility for the attack in a region has seen an increase in kidnappings for ransom. The statement did not say how old the abducted children are, but the term “pupil” in Nigeria usually refers to someone in kindergarten or primary school, covering ages up to 12.

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Banchereau reported from Dakar, Senegal.