Lagos - Nigerian President Muhammadu Buhari promised on Friday to free the remaining Christian schoolgirl still held by Boko Haram, as he prepared to meet the other Dapchi students released by the Islamist militants.Buhari is to meet the girls in Abuja later on Friday, after which they will undergo medical checks and counselling similar to that given to other former captives released by Boko Haram.A total of 104 of the 110 students seized from the school in Dapchi, in the northeastern state of Yobe, on February 19 were dropped off by the jihadists on Wednesday morning.Five other girls died on the day they were abducted, while the last one - a Christian called Leah Sharibu - is still with her captors, apparently because she refused to convert to Islam. "It is disheartening that one of the girls, Leah Sharibu, remains in captivity," said Buhari on his official Twitter account.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. "Let me assure that I am as committed to her freedom as I was to the girls' freedom when all 110 of them were in captivity," he said. "We will do everything in our power to bring Leah back safely."The girls - many dressed in matching fawn-coloured, long hijabs - boarded a Nigerian military transport plane from the Borno state capital Maiduguri to Abuja on Wednesday night.The Dapchi kidnapping revived painful memories in Nigeria of the April 2014 abduction of over 200 schoolgirls from Chibok, a town also in the north east, which caused global outrage. While some of the Chibok girls have been freed, a total of 112 remain in captivity.Boko Haram has repeatedly targeted schools giving a so-called Western education in the mainly-Muslim region as part of an insurgency that has killed at least 20 000 people since 2009.