Boko Haram group has claimed responsibility for the abduction of hundreds of students in an attack on a boys school in Nigeria's northwestern Katsina state, media reports said Tuesday. More than 330 students are missing from the Government Science Secondary School in Kankara after gunmen with assault rifles attacked their school Friday night, forcing hundreds of students to flee and hide in surrounding bushes and forest.

The Daily Nigerian said Tuesday it received an audio message from Boko Haram leader Abubakar Shekau, who was behind the 2014 abduction of hundreds of schoolgirls in Chibok, claiming that it was his group that abducted the schoolboys. There has been no independent verification of the audio message, but Shekau has over the past released video and audio messages on Boko Haram’s behalf.

Nigerian presidential spokesperson Garba Shehu said in a statement Monday that "the kidnappers had made contact and discussions were already on, pertaining to the safety and return" of the children to their homes. Shehu said nothing about the identity of the abductors.

Several armed groups operate in northwestern Nigeria where Katsina state is located. It was originally believed that the attackers were bandits, who sometimes work with Boko Haram.

The government said a joint rescue operation was launched Saturday by Nigeria’s police, air force and army after the military engaged in gunfights with bandits after locating their hideout in the Zango/Paula forest. Many of the more than 600 male students were able to escape during the attack while the police engaged in a gunfight, according to Katsina State police spokesperson Gambo Isah.

Boko Haram has in the past abducted students from schools. The most serious school attack took place in April 2014, when more than 270 schoolgirls were abducted from their dormitory at the Government Secondary School in Chibok in northeastern Borno State. About 100 of the girls are still missing, as The Associated Press (AP) reported.

The recent incident at the Government Science Secondary School in Kankara is the worst attack on a boys' school since February 2014, when 59 boys were killed during a Boko Haram attack on the Federal Government College Buni Yadi in Yobe State.

Boko Haram launched a bloody insurgency in 2009 in northeastern Nigeria but later spread its atrocities to neighboring Niger, Chad and Cameroon, prompting a military response. More than 30,000 people have been killed and nearly 3 million displaced in a decade of Boko Haram's violence in Nigeria, according to the U.N. Office for the Coordination of Humanitarian Affairs. Boko Haram violence has affected 26 million people in the Lake Chad region and displaced 2.6 million others, according to the U.N. Refugee Agency.