Authorities in Nigeria said Sunday that they have secured the release of 100 schoolchildren who were kidnapped from a Catholic school last month.

The Christian Association of Nigeria (CAN) said 315 pupils and staff were abducted by gunmen on November 21 from St. Mary's co-educational boarding school in the north-central Niger state.

Fifty students were able to escape in the following hours.

The fate of another 165 students and school staff, who are believed to still be in captivity, remains unclear.

What do we know about the 100 children who have been released?

The 100 schoolchildren who were released have arrived in the capital Abuja, a UN source told the AFP news agency. They will be handed over to local officials in Niger state on Monday, the source added.

Presidential spokesman Sunday Dare confirmed to AFP that the schoolchildren have been returned.

Local media, including broadcaster Channels Television, also reported on the release of the 100 children.

It was unclear whether the release was the result of military force or negotiations. It is also not known which group is responsible.

Niger state authorities as well as the CAN have said they have not been formally notified of the children's release. Nigeria's government has also not officially commented.

Spate of kidnappings shine spotlight on insecurity in Nigeria's north

For years, Nigeria has been fighting an Islamist insurgency in the northeast of the country, while gangs of so-called "bandits" carry out abductions and ransack villages in the northwest.

The country is still scarred by the 2014 kidnapping of nearly 300 schoolgirls by Boko Haram militants. Some of the former students, most of whom were between the ages of 16 and 18 at the time, are still missing.

But a recent surge in abductions since last month has again highlighted the West African nation's poor security situation. Last week, Mohammed Badaru Abubakar resigned as defense minister as authorities look to respond.

In November, 25 Muslim schoolgirls were kidnapped in the state of northwestern Kebi, as were 38 Christian worshipers and their pastor in Kogi state, in the North Central region.

In a separate incident in Sokoto state in the northeast, a bride and 10 of her bridesmaids were abducted from a village.

The kidnappings have coincided with US President Donald Trump ramping up the pressure on Nigeria over the alleged mass killings of Christians.

Trump has said a Christian "genocide" is unfolding in Nigeria and has threatened military action unless the government addresses the situation.

Nigeria's government has rejected Trump's claims.

Edited by: Dmytro Hubenko