On April 14, 2014, Boko Haram stormed a boarding school in Chibok city in northern Nigeria, abducting 276 schoolgirls.
Four years later, more than 100 of them remain in captivity.
Their families and activists from the Bring Back Our Girls movement continue to wait for news of the missing girls.
Bukky Shonibare, Bring Back Our Girls movement, said "The government has not done enough in bringing back the Chibok girls. Enough means having all of the girls come back. Its 4 years that we are having to commemorate now. Sadly and disappointingly so."
The Nigerian government, initially criticized for its apparent inaction following the kidnapping, then waged a "total war" against the extremist group.
Since then, some 100 girls have been released, with the authorities claiming that Boko Haram has been "defeated".
Though the armed group no longer controls the large swathes of Nigerian land it did a few years ago, the conflict continues to claim scores of lives.
Muhammadu Buhari, President of Nigeria, said "I want to appeal to the Chibok community never to lose hope or despair. We are determined as never before to bring back our remaining Chibok daughters. And this, we must accomplish. And that will be soon by God's grace."
A video broadcast by Boko Haram in January purportedly showed at least 14 of the Chibok schoolgirls claiming to have married off by the group's leader and vowing never to come home.
The mass abduction has grown to symbolize the sacrifice borne in the northeast, the epicenter of the crisis, where UNICEF reports nearly 1,400 schools have been destroyed and nearly 2,300 teachers killed since the start of the insurgency in 2009.