ABUJA, Nigeria (AP) — A wave of militant attacks on schools in Nigeria over the past week has left more than 80 children missing, local officials and a rights group said Sunday, the latest in school abductions in the West African country where the government is battling an array of jihadi and other armed groups.

The attackers targeted a primary school in the conflict-battered state of Borno, in Nigeria’s northeastern corner, sometime between Wednesday and Thursday. The militants abducted 42 children there, in the Askira Uba and Chibok areas.

Amnesty International said that attack took place in the village of Mussa near Sambisa Forest, a stronghold of militants from Boko Haram and its splinter group, an Islamic State affiliate known as the Islamic State West Africa Province.

Across the country, two secondary schools in the southwestern Oyo state were attacked hours apart on Friday, and at least 40 children were abducted there, according to Amnesty’s Nigeria branch. Such abductions are rare in this particular area.

The rights group warned on Sunday that the threat of abduction is forcing many children out of school, while underage girls are being pulled out of classrooms and forced into marriage by families seeking to protect them from school attacks.

Peter Wabba, a government official from Mussa, said on Sunday that he was told the “exact number” of children abducted in Oyo was 48.

"The government is assuring us that they are doing their possible best to see that these children are rescued but up till now, we are still waiting,” he told The Associated Press.

Amnesty also said that the authorities "never fulfill promises to investigate the incidents and bring the perpetrators to justice.”

“Victims and their families continue to be denied access to justice," it said.

On Saturday, police spokesperson Ayanlade Olayinka told the AP that three gunmen were detained in connection with the Oyo attack, which took place in the Oriire area, about 220 kilometers (135 miles) from the city of Lagos.

The suspects were identified by the community and arrested, Olayinka said. Police did not say if they were searching for more suspects.

Abductions of schoolchildren are common in Nigeria, Africa's most populous nation, especially in the country's north. Last year, two mass abductions from schools rocked the nation, with over 300 children taken in the northern region.

School kidnappings have come to define insecurity in Nigeria, and analysts say it’s often because armed gangs see schools as strategic targets they can exploit to draw more attention.