The families of more than 300 kidnapped Nigerian schoolboys fear they may be radicalised or held for years as security forces comb a vast forest for armed captors possibly from the jihadist Boko Haram movement.

According to an unverified audio clip, the group – whose name means “Western education is forbidden” – was responsible for last week’s raid on an all-boys school in the town of Kankara in northwestern Katsina state.

Parents worry time may be running out: Boko Haram has a history of turning captives into jihadist fighters.

“They will radicalise our children if the government does not act fast to help us rescue them,” said trader Shuaibu Kankara, crying as he spoke from home.

His 13-year-old son, Annas, was among those abducted from the Government Science school on Friday night.

Two other sons managed to escape when men on motorbikes with AK-47 assault rifles stormed the school and marched the boys into a forest.

Some experts feared the boys could be taken over the border into Niger or split into groups to make finding them harder.

Late on Wednesday (local time), Katsina state Governor Aminu Bello Masari told the BBC Hausa service the estimated 320 missing boys were in the forests of neighbouring Zamfara state.

Earlier in the day, an aide to Masari said soldiers and intelligence officers had been combing the Rugu forest, which stretches across Katsina, Zamfara, Kaduna and Niger states, in search of the boys.

Boko Haram and its offshoot, Islamic State West Africa Province, have waged a decade-long insurgency estimated to have displaced about 2 million people and killed more than 30,000. They want to create states based on their extreme interpretation of sharia law.

If Boko Haram carried out the kidnapping in an area where it had not previously claimed attacks, it would mark an alarming expansion beyond its northeastern base, security experts say.

But it may alternatively have purchased the boys from criminal gangs in the northwest with which it has been building ties.

Vincent Foucher, a security analyst at the French National Centre for Scientific Research, said Boko Haram earlier this year released videos in which it said groups in the northwest had pledged allegiance to its movement.

-AAP