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.
The sound of air raid sirens and explosions rang out in Ukraine's capital Kyiv on Sunday as German Chancellor Friedrich Merz arrived for a visit to show support for President Volodymyr Zelenskyy amid escalating Russian attacks.
Several people detained in India's Gen Z-led protests against voter roll changes
Indian police detained several people in the capital New Delhi on Saturday, disrupting a second day of protests backed by the Gen Z-led Cockroach Janta Party and other opposition groups against changes to voter rolls.
US Coast Guard finds debris from missing medical aircraft off Nantucket
The US Coast Guard said late on Saturday it found debris from a medical transport aircraft off the shore of Massachusetts' Nantucket island and was searching for six people who were on board.
Trump names intelligence chief as AI czar
US President Donald Trump has appointed Director of National Intelligence Jay Clayton as the administration's AI czar, the Wall Street Journal reported on Saturday, citing an interview with Clayton.
Trump shares Republican senator's phone number in feud over time switch
US President Donald Trump shared online the supposed phone number of a Republican US senator in the first of multiple posts on Saturday in a row over making daylight saving time permanent.
