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.
Iran and US agree to halt attacks and renew talks, US official says
Iran and the United States agreed to halt recent hostilities in the Gulf and renew talks regarding their dispute over the Strait of Hormuz, a US official said on Sunday, raising hopes of saving an interim peace deal that was under pressure from days of tit-for-tat strikes.
Italy and Balkans hit by heatwave as wildfire fears rise
Italy and the Balkans felt the impact on Monday of the record-breaking heatwave that has caused hundreds of excess deaths and disrupted daily life across the continent for more than a week, with growing concerns over the spread of wildfires.
Pakistan forces kill 29 militants in border operation, Kabul says dozens of civilians dead
Pakistan's security forces killed at least 29 militants in ground and air operations along the Afghanistan border, it said on Monday, while the Afghan Taliban said at least 38 civilians were killed in airstrikes.
Putin rejects Ukraine proposal to limit long-range strikes
Russian President Vladimir Putin says Moscow will continue its military push to fully capture four Ukrainian regions, rejecting what he described as a Ukrainian proposal to scale back long-range attacks.
Ousted Bangladesh PM Hasina vows to return home this year
Ousted former Prime Minister Sheikh Hasina has vowed to return to Bangladesh this year, brushing aside a death sentence handed down in absentia and denouncing the ruling as "illegal, unconstitutional and politically motivated".
