Ceremonies are to be staged around the world to mark one year since more than 200 girls were abducted by Nigerian militant Islamist group Boko Haram.
A procession is being held in the capital, Abuja, with 219 girls taking part to represent each missing girl.
The abduction of the girls in Chibok in north-eastern Nigeria sparked global outrage, with nations such as the US and China promising to help find them.
There have been sightings of the girls reported, but none has been found.
Boko Haram say the girls have converted to Islam and been married off. One witness told the BBC that she saw more than 50 of them alive three weeks ago in the north-eastern town of Gwoza.
It has been a whole year of agony for the relatives of the missing 219 Chibok girls. There have been a few sightings of some of the abducted students but very little official information from a government that has long promised to rescue them from the clutches of Boko Haram.
One mother told the BBC she sometimes arranges her 19-year-old daughter’s clothes in the hope that she is about to return home.
Read more: BBC News