Results from 120,000 polling stations in 36 states where voting was held Saturday were expected to trickle in to the capital Abuja after being collated at the state and local levels.
The chairman of the Independent National Electoral Commission (INEC), Mahmood Yakubu, will officially announce the outcome in the coming days.
Whoever becomes the next leader of Africa’s most-populous country and leading oil producer will face a daunting to-do list, from widespread insecurity and endemic corruption to an economy recovering from recession.
While INEC said it was “generally satisfied” with the vote, polling stretched into Saturday evening in areas where equipment failed to function or arrive on time.
It also remained unclear what INEC would do about the 8,500 polling places where voting wasn’t possible.
Civil society groups monitoring the vote reported 16 deaths from election-linked violence in eight of Nigeria’s 36 states.
Nigeria’s last election in 2015 was seen as free and fair but Idayat Hassan of the Centre for Democracy and Development (CDD) warned that this year’s bloodshed and malfunctions amounted to setbacks.
“This election was a serious deterioration from 2015,” she told AFP. “What we now expect from a credible, free and fair election was not there.”
– Awaiting victory –
The victor of the 2015 election was 76-year-old President Muhammadu Buhari, who declared on Saturday that he “would be the winner” of this year’s vote where he was standing for a second four-year term.
His chief opponent is Atiku Abubakar, a 72-year-old former vice-president making his fifth shot at the presidency.
Results trickling in from individual polling units on Sunday showed neither man with a commanding lead, but offered snapshots of each candidate’s performance.
Abubakar failed to win the polling station where he voted in Yola, capital of his home state Adamawa.
While Buhari personally cast a ballot in his hometown Daura in the northern Katsina state, it remained unclear if he had won the polling unit set up for the presidential villa in the capital Abuja.
Originally set for February 16, INEC delayed at the last minute the presidential election to February 23, angering voters who had already travelled home to participate.
The delay saw the main parties accuse each other of conspiring with INEC to rig the result, although neither has produced evidence.
– Poll violence –
In the early hours before Saturday’s vote started, Boko Haram’s Islamic State-backed faction launched a rocket attack on the northeastern city of Maiduguri that killed one soldier.
There were several clashes between jihadists and soldiers elsewhere in Yobe and Borno states, where more than 500 Chadian troops arrived as backup.
In Rivers State in the southern Niger Delta, troops killed six “hoodlums” in a clash that left one soldier dead, the army said in a statement.
Abiodun Baiyewu, director of Global Rights Nigeria, a civil society group monitoring the vote, said the electoral commission and security forces could have done more.
“INEC needed to have a communication plan with security but we found that this was lacking and security was ineffective,” he said.
– Campaign promises –
A total of 72.7 million people with voter identity cards were eligible to vote in the polls. Parliamentary elections were held at the same time.
In 2015, former military ruler Buhari became the first opposition candidate in Nigerian history to defeat a sitting president, beating Goodluck Jonathan by 2.5 million votes.
Buhari has again vowed to be tough on insecurity and corruption, and wants to complete much-needed infrastructure projects.
Abubakar is a pro-business free marketeer whose main pledges have been to privatise giant state-run companies and float the embattled naira currency.
Nigerian elections have previously been characterised by voting along ethnic and religious lines.
But with Buhari and Abubakar both northern Muslims, that could split the northern vote, making southern states a key battleground.
Download our app and read this and other great stories on the move. Available for Android and iOS.