Nigerians were still voting in a few parts of the country after glitches prevented them from doing so on Saturday, but results of the national election would start to be announced from 6pm (5pm Irish time) the electoral commission said.
Counting was already underway in the West African oil exporting country's presidential and parliamentary elections, with the final tally expected within five days.
Commission chairman, Mahmood Yakubu, told a news briefing in the capital Abuja that collated results from a handful of Nigeria's 36 states would be announced from Sunday evening.
The race to succeed Nigerian president Muhammadu Buhari was expected to be the closest in Nigeria's history, with candidates from two parties that have alternated in power since the end of army rule in 1999 facing an unusually strong challenge from a minor party candidate popular among young voters.
A Reuters reporter saw people casting their votes at polling stations in Yenagoa city, in Nigeria's oil-producing south, where polling could not take place in some parts on Saturday because election officers and materials did not arrive.
In one, voters stood on sandy, weed-choked ground checking for their names plastered on a half-built concrete house.
"The experience was the yesterday it was a terrible thing," Freedom Amienyo, a 59-year-old civil servant, said after voting.
"But today they tried to redeem the situation and we have come exercise our franchise, which makes me happy".
Voting was also expected to continue in some parts of northeastern Borno state after voting machines failed to work.
It was not clear how many of Nigeria's 93 million registered voters were unable to cast a ballot on Saturday.
In most parts of the country of 200 million people, voting went smoothly. Despite scattered incidents of violence and intimidation, this was not on the scale of previous elections.
There were reports of violence in the northern state of Kano on Sunday, where an armed group attacked a collation centre in the town of Takai, before security forces arrived, said Rakiya Muhammad, an election observer who witnessed the incident.
Three horse race
The main presidential contenders are former Lagos governor Bola Tinubu (70) of the ruling All Progressives Congress, former vice president Atiku Abubakar (76) of the main opposition Peoples Democratic Party, and former Anambra State governor Peter Obi (61) of the smaller Labour Party.
Outgoing Mr Buhari, a retired army general who was also once a military ruler in the 1980s, is stepping down after winning two previous elections and serving the maximum eight years permitted by the constitution.
Whoever wins will face a litany of crises gripping Africa's top oil producer and the continent's most populous nation.
Nigeria is struggling with Islamist insurgencies in the northeast, an epidemic of kidnappings for ransom, conflict between herders and farmers, shortages of cash, fuel and power, as well as deep-rooted corruption and poverty.
"I witnessed the worst experience of my life under this administration. Recently I spent two days without eating anything," said Ahmad Sulaiman (49), who sells handbags in a market, as he stood in the baking sun in a dusty alleyway in Kano city.
"I voted because I wanted change," he added, declining to say who he had voted for.
