Aisha Yesufu is the chairwoman of the strategic committee of the Bring Back Our Girls campaign in Abuja.
"We keep on hoping that the girls will be found. We will keep up the fight, there will be no retreat, no surrender on the Chibok girls until each one of them is accounted for," she told DW.
Activists have organized numerous events this week to mark the 500 days of the disappearance of the more than 200 girls. They included Muslim and Christian prayer services, a tree planting ceremony and a march through Abuja.
The ordeal began when Boko Haram fighters stormed the Government Secondary School in the remote town of Chibok in Borno State on April 14, 2014.
President Buhari meets Bring Back Our Girls campaigners
The insurgents seized 276 girls who were preparing for exams. 57 escaped but nothing has been heard of the remaining 219 since May 2014 when about 100 of them appeared in a Boko Haram video dressed in Muslim attire and reciting the Koran.
The mass abduction brought the brutality of the Islamist insurgency unprecedented global attention. #BringBackOurGirls demanded their release and went viral on social media, attracting support from US First Lady Michelle Obama and many others.
The Nigerian military has said it knows where the girls are but has ruled out a rescue effort because it would put the girls' lives in jeopardy.
Deutche Welle
