Nearly 300 schoolgirls were abducted from the remote Nigerian town of Chibok a year ago. Dozens of the girls escaped but 219 remain missing.

The kidnapping provoked international outrage, but the majority are still missing despite Western pledges to help track them down and a Chadian attempt to broker their release.

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April 30, 2014: Women react during a protest outside Nigeria's parliament in Abuja demanding security forces search harder for the schoolgirls abducted by Islamist militants two weeks previouslyAfolabi Sotunde/Reuters
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May 7, 2014: Michelle Obama backs the #bringbackourgirls Twitter campaign@Flotus
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May 12, 2014: A woman takes part in a protest at the Unity fountain in Abuja, calling for the release of the abducted secondary school girls in the remote village of ChibokAfolabi Sotunde/Reuters
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May 15, 2014: A student who escaped when Boko Haram rebels stormed a school and abducted schoolgirls, identifies her schoolmates from a video released by the Islamist rebel group at the Government House in Maiduguri, Borno StateReuters
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May 15, 2014: A woman shouts during a vigil in Abuja calling for the release of the Nigerian schoolgirls abducted in the remote village of ChibokJoe Penney/Reuters
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May 21, 2014: Chiroma Maina holds a picture of her abducted daughter Comfort Amos, as she sits with her husband Jonah and her daughter Helen, at their home in MaiduguriJoe Penney/Reuters
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June 2, 2014: Schoolgirls who escaped from Boko Haram kidnappers in the village of Chibok wait at the government house in Maiduguri to speak with State Governor Kashim ShettimaAFP
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June 5, 2014: US congressman Louie Gohmert speaks with three girls who escaped after they were abducted in Chibok, at a news conference in LagosAkintunde Akinleye/Reuters
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June 5, 2014: Hauwa Nkaki, mother of one of more than 200 girls abducted in Chibok, cries during a news conference in LagosAkintunde Akinleye/Reuters
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July 22, 2014: Nigerian President Goodluck Jonathan speaks to some of the Chibok schoolgirls who escaped their Islamist captorsWole Emmanuel/AFP
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September 19, 2014: One of the escaped schoolgirls kidnapped by Boko Haram shares the story of her capture and escape during a press conference at the Hudson Institute in Washington, DCPaul J Richards/AFP
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October 14, 2014: Isaac Rebecca, one of the girls who escaped from the Boko Haram camp, speaks during a protest held in Abuja to commemorate the six-month anniversary of the abduction of the Chibok girlsReuters
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A policewoman reacts during a protest march held in Abuja on the six-month anniversary of the abduction of the Chibok schoolgirlsAfolabi Sotunde/Reuters
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January 1, 2015: Rebecca Samuel, mother of Sarah, one of the abducted Chibok schoolgirls, reacts while speaking at a meeting to review efforts to recover the abducted Chibok girls in AbujaAfolabi Sotunde/Reuters
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January 1, 2015: Nkeki Mutah, father of one of the abducted schoolgirls, cries as he addresses a meeting to review efforts to recover the abducted Chibok girls, in AbujaAfolabi Sotunde/Reuters
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February 25, 2015: Protesters reflect on Day 301 of the #BringBackOurGirls campaign in AbujaAfolabi Sotunde/Reuters

Nigeria's President-elect Muhammadu Buhari has vowed to make every effort to free the schoolgirls abducted by Boko Haram militants a year ago but admitted it was not clear whether they would ever be found.

Boko Haram's leader, Abubakar Shekau, claims the girls had been "married off" to his fighters. The name of Nigeria's home-grown Islamic extremist group means "Western education is forbidden" or sinful.

Boko Haram Islamic militants have kidnapped at least 2,000 girls and women since the start of 2014, turning them into cooks, sex slaves and fighters, and sometimes killing those who refused to comply, Amnesty International said.

About 800,000 children have been forced to flee fighting, according to Unicef. The number of children absent from primary school in Nigeria has increased from eight million in 2007 to 10.5 million – the highest figure in the world, it says.