LAGOS, Nigeria

Terror group Boko Haram has claimed responsibility for the weekend kidnapping of about 500 students from a public school in northwestern Nigeria.

In four-minute audio on Tuesday, the group said it was behind the abduction in Kankara, a small town in Katsina State.

"Our brothers are behind the kidnapping in Katsina," said a voice on the recording identifying himself as Abubakar Shekau, Boko Haram’s leader.

Multiple military sources said security officials are investigating the claim.

About 500 boys were abducted from the Government Science Secondary School late Friday. Residents and survivors said the abductors rode to the school in about 100 motorbikes, firing assault rifles to escape into the bush after dividing the boys into groups.

Nigerian President Muhammadu Buhari has ordered an immediate rescue operation.

At least 17 of the students were rescued on Monday after a gun battle between military forces and the armed group, according to Aminu Masari, Katsina’s governor.

The incident has triggered condemnation across the world.

UN Secretary-General Antonio Guterres said the attack "constitutes grave violations of human rights."

The attack was the third abduction of students in over a decade of Boko Haram terror attacks in the country following the 2014 kidnapping of 270 Chibok schoolgirls and the 2018 abduction of 110 girls in a parking school in the northeast.