A student footwear IS left behind after gunmen abducted students at the Government Science school in Kankara, in northwestern…
Students' shoes are left behind after gunmen abducted hundreds of boys at the Government Science School in Kankara, in northwestern Katsina state, Nigeria, Dec. 15, 2020.

ABUJA - Nigerian terrorist group Boko Haram claimed responsibility Tuesday for the abduction of more than 300 schoolboys last Friday in northwestern Nigeria. 

Nigerian authorities have yet to respond to the claim. However, the Katsina State governor on Monday said he had begun negotiating with the kidnappers. 

Security expert Kabir Adamu believes bandits, not Boko Haram, abducted the schoolboys. 

Nigerian soldiers walk inside the Government Science where gunmen abducted students in Kankara, in northwestern Katsina state, Nigeria, Dec. 15, 2020.

"We're of the opinion that (Boko Haram) did not carry out the abduction," Adamu said. "It was carried out by bandits, but it is a known fact that (the) group has reached out to these bandits and has attempted to recruit them." 

Boko Haram and its splinter group, the Islamic State of West Africa Province, operate predominantly in the Nigeria's northeast, while bandits initially blamed for the attack operate in the country's northwest. 

But the claims by Boko Haram raise concerns that the group may be expanding its terror campaign to other regions, Adamu said. 

"There have been videos emerging from forested parts of the northwest with some of these bandit groups claiming allegiance to (Boko Haram sect leader Abubakar) Shekau, and he himself has shown that he's interested in expanding his territorial enclave up to the northwest," Adamu said.

An empty dormitory full of schoolboys' belongings is seen after gunmen abducted students at the Government Science School in Kankara, in northwestern Katsina state, Nigeria, Dec. 15, 2020.

At least 333 students are still missing after some of the boys escaped to safety the night of the attack. 

Nigerian security forces said on Monday they had surrounded a hideout suspected to be the den of the kidnappers. However, rights groups continue to point fingers at authorities, saying government corruption has enabled terrorism to linger in Nigeria. 

Last week, the International Criminal Court said it will launch a full-blown investigation on war crimes committed by Boko Haram and the Nigerian military following several calls from groups such as Amnesty International. 

"These attacks are crimes under international law," said Seun Bakare, a spokesperson at the human rights group. "They're a direct attack on the right to education, and the government must swiftly rescue these school kids and, in addition to that, bring perpetrators to book." 

Nigerian President Muhummadu Buhari promised to prioritize the fight against insurgency during his campaign for office in 2015. But five years later, the country's security situation continues to worsen.