LAGOS, Nigeria (AP) — Gunmen have released 15 more students who were abducted from their high school in northern Nigeria last month, authorities said Sunday. The kidnappers are believed to still be holding 65 others taken from the school.

The students were released Saturday night, said John Hayab, chairman of the Christian Association of Nigeria in Kaduna state, whose son attends the school where the hostages were taken.

Samuel Aruwan, the Kaduna state commissioner for internal security and home affairs, told The Associated Press that the government had been briefed about the release.

He did not provide further details, but local media have reported in the past that the gunmen demanded a ransom of N500,000 ($1,220) for each student in exchange for their freedom.

Gunmen abducted the students from the Bethel Baptist High School in the northern town of Damishi on July 5. The kidnappers had previously released a group of 28 hostages and before that 34 others.

As parents of the freed students celebrated their release Sunday, hundreds of others still awaited word on their children's fates across northern Nigeria.

More than 1,000 students have been forcibly taken from their schools across six states in northern Nigeria since December, according to an AP tally of figures previously confirmed by the police.

Although most of those kidnapped have been released, some are still held by their abductors. The kidnappings have forced some state governments to temporarily close schools.

The abductors, known locally as bandits, often target schools in remote areas where there is no adequate security presence.