Five more students who were kidnapped by gunmen from a school in Nigeria three months ago have been released after ransoms were paid, the school administrator said.

About 150 students went missing after armed men raided the school in Kaduna state in Nigeria's northwest in July, the 10th mass school kidnapping since December. 

Such kidnappings at schools in Nigeria were first carried out by jihadist group Boko Haram, and later its offshoot Islamic State West Africa Province, but the tactic has since been adopted by criminal gangs seeking ransom, according to authorities.

The bandits have been releasing the students in batches after getting ransom payments.

Reverend John Hayab, the administrator of the Bethel Baptist High School, said after the latest release, four students remained in captivity and the school was working to ensure they were freed soon.

"No student was released for free," he told Reuters late on Friday. He declined to say how much was paid.