LAGOS, Nigeria (AP) — Nigeria’s Boko Haram jihadist rebels have claimed responsibility for the abduction of hundreds of students in one of the largest attacks in years on a boys’ school in northern Katsina state.

More than 330 students are missing from the Government Science Secondary School in Kankara after gunmen with assault rifles attacked their school Friday night.

The government and the attackers are negotiating over the fate of the boys, according to Nigerian presidential spokesman Garba Shehu.

“The kidnappers had made contact and discussions were already on, pertaining to the safety and return” of the children to their homes, said Shehu on Twitter Tuesday. He gave no information about the identity of the abductors.

The Daily Nigerian said it received an audio message from Boko Haram leader Abubakar Shekau saying that his group abducted the schoolboys because Western education is against the tenets of Islam.

“What happened in Katsina was done to promote Islam and discourage un-Islamic practices as Western education is not the type of education permitted by Allah and his Holy Prophet,” the paper quoted Shekau as saying.

There has been no independent verification of the audio message but Shekau has in the past released video and audio messages on Boko Haram’s behalf.

Several armed groups operate in northern 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 attackers were in a gunfight with police, according to Katsina State police spokesman Gambo Isah.

Boko Haram has in the past abducted students from schools.

Nigeria's 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. Boko Haram said at the time that it wanted to stop women from attending schools.

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.

The assault comes as Boko Haram and the Nigerian military may be investigated for war crimes in the insurgency, which has lasted more than 10 years.

The International Criminal Court’s chief prosecutor last week said a decade-long probe has found enough evidence to merit opening a full-scale investigation into allegations of war crimes and crimes against humanity by Boko Haram extremists as well as into charges that the Nigerian government forces have also perpetrated abuses.

Prosecutor Fatou Bensouda said there is a “reasonable basis to believe” Boko Haram and splinter groups linked to it committed crimes including murder, rape, sexual slavery and torture, as well as intentionally targeting schools and places of worship and using child soldiers. While a vast majority of the criminality in the conflict has been carried out by Boko Haram, prosecutors also found grounds to believe members of Nigeria’s security forces had committed crimes, she said.

Amnesty International last week released a report saying at least 10,000 civilians have died in Nigerian military custody since 2011 after being detained in connection with the Boko Haram insurgency in northern Nigeria.

Boko Haram and the breakaway faction, the Islamic State West Africa Province, are fighting to impose strict Islamic Shariah rule in Nigeria.

Thousands have been killed in the more than 10-year-old insurgency and more than a million people displaced.