Three years ago, the abduction of more than 200 schoolgirls by the jihadist group Boko Haram in Chibok in northeastern Nigeria sparked global outrage and a celebrity-backed campaign #bringbackourgirls.
For more than two years there was no sign of the girls who were kidnapped by the Islamist fighters from their secondary school in Chibok in northeastern Borno State in April 2014.
But the discovery of one of the girls with a baby last May raised hopes for their safety, with a further two girls found in later months and a group of 21 released in October in a deal brokered by Switzerland and the International Red Cross.
Nigeria is facing mounting pressure to find the estimated 195 girls still held captive by the jihadist group.
Here are 10 key facts about the Chibok schoolgirls and Boko Haram:
* Since 2009, Boko Haram has waged an insurgency to carve out an Islamic state in northeast Nigeria that has killed at least 20,000 people and displaced more than two million.
* The most high-profile attack took place on April 14, 2014, when Boko Haram kidnapped 276 schoolgirls from a secondary school in Chibok in northeast Borno state. Around 50 of the girls escaped in the initial melee but 219 were captured.
* Nigeria’s government and military, then under the command of former president Goodluck Jonathan, faced heavy criticism for their handling of the incident, with towns and cities across the nation witnessing protests.
* The kidnappings sparked a strong social media reaction, with the phrase #bringbackourgirls tweeted around 3.3 million times by mid-May 2014, and the global campaign which followed backed by then U.S. First Lady Michelle Obama.
* Hope for the girls was briefly raised in April 2015 when the Nigerian military announced it had rescued 200 girls and 93 women from the Sambisa forest, northeast of Chibok. It was later revealed that the Chibok girls were not among them.
* One of the Chibok girls, Amina Ali, was rescued in May. Held for months by the Nigerian government, she told her mother that the girls were starved and resorted to eating raw maize, and that some had died in captivity, suffered broken legs or gone deaf after being too close to explosions.
* At least 2,000 girls and boys have been kidnapped by Boko Haram since the beginning of 2014, according to Amnesty International, which says they are used as cooks, sex slaves, fighters and even suicide bombers.
* Boko Haram have used 27 children to carry out suicide attacks in West Africa in the first three months this year, almost surpassing the total of 30 child bombings during 2016, said the U.N. children’s agency UNICEF.
* Nigeria is in talks with Boko Haram militants over the release of more of the abducted Chibok girls, according to a mediator involved in the discussions.
* The militants split last year with one faction moving away from the group’s established figurehead Abubakar Shekau over his failure to adhere to guidance from Islamic State to which Boko Haram pledged allegiance in 2015.