Citizens are going to the polls today after a last-minute postponement earlier this week.
The main challenger to reigning president Muhammadu Buhari is former Vice-President Atiku Abubakar.
It is not known exactly when the final results will be announced.
Experts say a winner could be declared as late as Tuesday.
Nigeria is Africa's most populated country.
Hope for progress after US, Iran hold first shuttle talks in months
The first shuttle talks between the US and Iran for months raised hopes on Wednesday that the adversaries could make some progress towards ending the Middle East war, although neither side spelled out any change in their positions.
Four killed in Gaza in strikes, Israel says it killed a Hamas finance chief
Israeli airstrikes killed at least four Palestinians in the Gaza Strip on Wednesday, local health officials said, and Israel said one of the attacks targeted a Hamas finance chief.
Philippine Senate lowers threshold for conviction in VP Duterte's impeachment trial
The Philippine Senate, sitting as an impeachment court, on Wednesday lowered the number of votes needed to convict Vice President Sara Duterte, reducing the threshold prosecutors must clear to secure a guilty verdict.
Pakistan tightens security ahead of march planned by Imran Khan's party
Pakistan curbed access on Wednesday to its capital, Islamabad, ahead of a march planned by supporters of jailed former Prime Minister Imran Khan, blocking major highways with shipping containers and deploying tens of thousands of security forces.
Search continues after death toll from capsized Indonesia ship rises to 20
The official death toll from a passenger ship that capsized and sank in Indonesia's Java Sea rose to 20 on Wednesday, up from the previous 10, with rescuers expecting to find more bodies as the ongoing underwater search widens, officials said.
