Saturday's election is being seen as the closest race in the country's history, with President Goodluck Jonathan facing a strong challenge from former military ruler Muhammadu Buhari.
The election was postponed six weeks ago because Nigeria's military said it was unable to provide security as its soldiers were committed to the fight against Boko Haram.
On Friday, the military claimed it had destroyed the headquarters of Boko Haram in Gwoza, a town in northeast Nigeria.
Speaking on Premier's News Hour, Dr Khataze Gondwe from Christian Solidarity Worldwide said: "We're hearing this morning that the so called capital of their caliphate, Gwoza has fallen to Nigerian troops. It was thought that the girls from Chibok who were kidnapped and other captives were being held there. We're still waiting to hear more information."
Thousands of people have been killed since 2009, when the group began its insurgency to create an Islamic state, and gained worldwide attention last year when it was responsible for abducting at least 200 schoolgirls
The country is almost evenly split between a largely Christian south and a Muslim-majority north with Jonathan and Buhari pulling support from their respective regions.
President Goodluck Jonathan's People's Democratic Party (PDP) has ruled Nigeria since the return from military to civilian rule in 1999.
Dr Khataze Gondwe, CSW: