Gunmen have kidnapped scores of children from an Islamic seminary in central Nigeria in the latest in a wave of mass abductions that have forced some northern states to close public schools. The kidnappings come three years after 111 schoolgirls were snatched by jihadists from Dapchi and seven after Boko Haram extremists shocked the world by taking 276 girls from Chibok. We look at the mass raids which have become a hallmark of criminal gangs and extremist Islamist groups in Nigeria, with many of the Chibok girls still missing. – Snatched from their beds – Boko Haram gunmen seize 276 girls aged between 12 and 17 from the Government Girls Secondary School in the remote town of Chibok in Borno state on April 14, 2014. The girls are forced from their dormitories onto trucks and driven into the bush. Fifty-seven manage to flee in a daring escape. – ‘Slave brides’ – Boko Haram leader Abubakar Shekau claims responsibility in a video and vows to sell the girls as slave brides. The group says they have converted to Islam and will not be released unless militant fighters held in custody are freed. An international outcry follows with a campaign demanding the girls’ release backed by A-list celebrities and politicians, with the hashtag #BringBackOurGirls going viral. – First girl found – In April 2016, on the eve of the abduction’s second anniversary, a “proof of life” video emerges showing 15 of the girls in black hijabs. The following month the Nigerian army confirms the first of the schoolgirls has been found. Aged 19, she has a four-month-old baby and is found with a man she describes as her husband near Boko Haram’s Sambisa forest enclave. In October, 21 of the girls are freed following talks brokered by Switzerland and the International Committee of the Red Cross. Local sources say four jihadist prisoners were freed in return. – 82 freed – In May 2017 another 82 girls are released in exchange for five Boko Haram commanders. Later that month, Boko Haram release a video in which a woman in a black veil claiming to be one of the Chibok girls brandishes a gun and proclaims loyalty to the group. In all, 107 of the 219 held since 2014 have either escaped or been released. Some of the young women are now studying at the American University of Nigeria in Yola, although others had to drop out of education because their poverty-striken families could not afford to pay for transport, food or even their sanitary towels. – New mass abduction – In February 2018 the Islamic State West Africa Province (ISWAP), an offshoot of Boko Haram, snatches 111 girls from their boarding school in the northeastern town of Dapchi, around 300 kilometres (186 miles) from Chibok. The jihadists returned more than 100 girls to the town on March 21 after talks with the government. Five of their schoolmates reportedly died in captivity. But the group refused to free Leah Sharibu, then 15, because she would not convert to Islam. The only Christian among the hostages, she still remains in captivity three years on. – 333 boys taken – Late on December 11 more than 100 gunmen on motorcycles stormed the all-boys Government Science Secondary School in the town of Kankara, in Katsina state. The attack was intially blamed on armed criminals before Boko Haram — which operates hundreds of miles away — claimed responsibility. The boys were later released after talks with government officials. – 300-plus girls grabbed – Armed bandits raided a school dormitory in Jangebe in northwestern Zamfara state in February, where 300 girls were reported missing. It came just a week after gunmen stormed a school in nearby Niger state killing one student and kidnapping 42 pupils, teachers and relatives. In March gunmen kidnapped 39 students from a college outside the northwestern city of Kaduna. – Students killed to force ransom – Then on April 20, gunmen killed a member of staff as they stormed Greenfield University, also taking around 20 students. Five were killed a few days later to force families and the government to pay a ransom. Fourteen were released on Saturday after 40 days in captivity. On Sunday scores of children are taken from an Islamic school in Niger. Six northern states have shut schools since the end of last year in a bid to stop the attacks.