Armed attackers have killed a police officer and kidnapped at least 80 students and five teachers from a school in the northwestern Nigerian state of Kebbi, police, residents and teachers said.

The attack took place on the Federal Government College in the remote town of Birnin Yauri in Kebbi State on Thursday. It is the third assault by armed gangs on a school or college in Nigeria in less than a month which have been attributed by the authorities to bandits seeking ransom payments.

Usman Aliyu, a teacher at the school, said the gunmen took more than 80 students, most of them girls.

“They killed one of the (police officers), broke through the gate and went straight to the students’ classes,” he told Reuters news agency.

A spokesman for the police in Kebbi State, Nafiu Abubakar, said one officer had been shot dead during an exchange of fire between the police and the attackers, and a student had also been shot and was receiving medical treatment.

Abubakar said security forces were searching a nearby forest for the abducted students and teachers.

Police late on Thursday had not released the number of students missing, and a spokesman for the Kebbi state governor said they were conducting a tally of the missing.

Atiku Aboki, a local resident who went to the school shortly after the gunfire stopped, told Reuters he saw a scene of panic and confusion as people searched for their children.

“When we got there, we saw students crying, teachers crying, everyone is sympathising with people,” he said by telephone.

“Everyone was confused. Then my brother called me [to say] that his two children have not been seen and [we] don’t know if they are among the kidnapped.”

Heavily armed criminal gangs, known locally as bandits, have long targeted central and northwestern states, raiding villages, stealing cattle and kidnapping for ransom.

But they have increasingly targeted schools, snatching students or schoolchildren and herding them into forest hideouts to negotiate ransom payments.

More than 700 children and students have already been kidnapped by these gangs for ransom since December.

The raids have mostly taken place in the northwestern region. They are separate from armed operations centred on the northeast, where the Boko Haram group made global headlines in 2014 when it abducted more than 270 schoolgirls from the town of Chibok.

At the end of May, armed men seized 136 children from an Islamic seminary in central Nigeria’s Niger state.

The mass kidnappings are just one challenge for President Muhammadu Buhari’s security forces, which are also fighting an armed conflict in the northeast and rising separatist tensions in the country’s southeast.