Armed kidnappers in Nigeria have released 28 of the 120-plus students who were abducted at the beginning of July from the Bethel Baptist High School in the northern town of Damishi.

Church officials handed the children over to their parents at the school on Sunday.

But the Israel Akanji, president of the Baptist Convention, said more than 80 other children are still being held by the gunmen.

So far 34 children kidnapped from the school on July 5 have either been released or have escaped from the custody of the gunmen.

It is unclear when the other children will be released. The gunmen have reportedly demanded 500,000 Naira () for each student.

Mr Akanji said the church did not pay any ransoms because it is opposed to paying criminals, but he added the church was unable to stop the children's families from taking any actions they deem fit to secure their release.

A spokesman for the Nigerian Police, Mohammed Jalige, said security forces and civilian defence forces were on a routine rescue patrol on July 12 around the forests near the village of Tsohon Gaya when they found three exhausted kidnap victims roaming in the bush.

Two other students escaped on July 20 when they were ordered to fetch firewood from a nearby forest. Mr Jalige said they were undergoing medical examinations.

Gunmen have carried out a spate of mass abductions from schools in northern Nigeria this year, mainly seeking ransoms.

Nigerian President Muhammadu Buhari, who won election on hopes that he would tackle Nigeria's security challenges, has not been able to do much in addressing the growing cases of mass abductions from schools.