About 150 students are missing after armed men raided a boarding school in Nigeria's Kaduna state.

The attack is the 10th mass school kidnapping since December in northwest Nigeria, which authorities have attributed to armed bandits seeking ransom payments.

Police said gunmen shooting wildly attacked the Bethel Baptist High School in the south of Kaduna state overnight.

"They overpowered the school's security guards and made their way into the students hostel where they abducted an unspecified number of students into the forest," a police statement said, adding 26 people, including a female teacher, had been rescued.

Reverend John Hayab, a founder of the school, told Reuters about 25 students had managed to escape while the school's other students remained missing.

Roughly 180 students attended the school and were in the process of sitting exams.

The unrest has become a political problem for the Nigerian President

Local residents who declined to be identified told Reuters that security officials had cordoned off the school after the attack, which took place between 11pm on Sunday and 4am on Monday morning.

Armed men, known locally as bandits, have made an industry of kidnapping students for ransom in northwest Nigeria, with Kaduna state particularly hard hit. They have taken nearly 1,000 people from schools since December last year, more than 150 of whom remain missing.

Kidnappers have also targeted roads, private residents and even hospitals; in the early morning hours of Sunday, gunmen abducted six people including a one-year-old child from a hospital in northern Kaduna state.

School kidnappings in Nigeria were first carried out by jihadist groups Boko Haram and Islamic State West Africa Province, but the tactic has now been adopted by other gunmen.

In February, President Muhammadu Buhari urged state governments "to review their policy of rewarding bandits with money and vehicles," warning that the policy might boomerang disastrously.

The unrest has become a political problem for Buhari, a retired general and former military ruler who has faced mounting criticism over prominent attacks by the gangs.

The highest profile school kidnapping was that of more than 270 schoolgirls abducted by Boko Haram from the town of Chibok in 2014.

Around 100 of them remain missing.