Suspected Boko Haram militants have kidnapped 25 girls from a remote village in northeast Nigeria witnesses have claimed.
This is despite talks to free hostages already held by the group.
Nigeria has been declared officially free of Ebola after a 42-day period with no new cases, the World Health Organisation (WHO) has said.
The announcement eases fears that the disease could have spread to one of Africa's most densely-populated areas.
WHO Director General Dr Margaret Chan said on Sunday that the appearance of the virus in Lagos would have been "the worst nightmare scenario anyone could imagine".
She said the nation's innovative polio campaign, which uses satellite technologies to track population, had been re-purposed to aid the fight against Ebola.
Last week, the WHO announced that Senegal was Ebola-free, but the pace of the outbreak continues to quicken in the three worst-hit countries.
The residents of the home town of over 200 kidnapped Nigerian schoolgirls are a cautiously optimistic about a ceasefire with the Islamic extremists who kidnapped their daughters six months ago.
"We don't know how true it is until we prove it," Bana Lawan, chairman of the Chibok local government area, said.
"We will know the negotiations were successful when we see the girls physically. And then we will know it is true. And then we will celebrate."
Community leader Pogu Bitrus said "people rejoiced, but with caution" after the military announced the ceasefire with the Islamic extremist group Boko Haram on Friday.
"We are waiting, hoping that it is really true and that the people who negotiated on Boko Haram's side, that they are the genuine leaders."
However, Suspected Boko Haram militants have killed several people in two attacks on Nigerian villages that occurred after a government announcement of a ceasefire, security sources and witnesses said.
Suspected insurgents attacked the village of Abadam, killing at least one person and ransacking homes.
Another attack on the village of Dzur left at least eight people dead.
Nigeria's armed forces chief, Air Chief Marshal Alex Badeh, announced on Friday a deal with Boko Haram for a ceasefire.
Nigeria aims to have around 200 girls kidnapped by Islamist Boko Haram militants freed by Tuesday, according to a senior source at the presidency.
The source was speaking to Reuters news agency but he declined to comment on where the transfer would take place.
He said: "I can confirm that the federal government is working hard to meet its own part of the agreement so that the release of the abductees can by effected either on Monday or latest Tuesday next week."
Boko Haram could release 200 missing Nigeria schoolgirls within 'hours or days' after being abducted by the terror group six months ago.
Nigerian defence spokesman Major General Chris Olukolade said the deal was still being negotiated.
But French President Francois Hollande welcomed the "good news" and told a news conference in Paris the girls' release "could happen in the coming hours and days".
France has been involved in negotiations that led to the release of several of its citizens kidnapped by Boko Haram in Cameroon.
Boko Haram negotiators have assured that the schoolgirls and all other people in their captivity are all alive and well.
A senior Nigerian security source confirmed the existence of talks to Reuters, but said it remained unclear whether Abuja was negotiating with self-proclaimed Boko Haram leader Abubakar Shekau, or another faction within the group.
"Commitment among parts of Boko Haram and the military does appear to be genuine. It is worth taking seriously," the security source told Reuters.
Talks have failed before in part because the group has several different factions.
The government was negotiating with Danladi Ahmadu, a man calling himself the secretary-general of Boko Haram, the presidency source said. It was not clear if Ahmadu is part of the same faction as Shekau.
Nigerian presidential aide Hassan Tukur said the agreement followed a month of negotiations, mediated by Chad.
He told BBC Focus on Africa that Boko Haram had announced a unilateral ceasefire on Thursday and the government had responded.
"They've assured us they have the girls and they will release them," he said.
"I am cautiously optimistic."
The schoolgirls kidnapped from Chibok School six months ago will be released by Boko Haram as part of a ceasefire agreement, the Presidency has announced.
The Nigerian government has agreed a ceasefire with the militant Islamic group Boko Haram, the Presidency has said.