- By Nduka Orjinmo
- BBC News, Abuja
The votes are counted in Nigeria’s tightest presidential election since the end of military rule in 1999.
Voting was marred by long delays as polling stations failed to open on time in some areas due to logistical issues and security incidents.
Turnout appeared to be high, with many young, new voters arriving before dawn to cast their ballots.
The elections are the largest democratic exercise in Africa, with 87 million eligible voters.
Politics has been dominated by two parties – the ruling APC and the PDP – since the restoration of multi-party democracy 24 years ago.
But this time there is also a strong challenge from a third party candidate in the race to succeed President Muhammadu Buhari – Peter Obi of the Labor Party, who is supported by many young people.
Tens of thousands of polling stations are counting the results, which will be collected and sent to the election headquarters in the capital Abuja.
The final result is expected at least on Tuesday.
At a press conference, the election leader, Mahmood Yakubu, apologized for the delays in voting, but said anyone standing in line at 13:30 GMT (14:30 local time) would be allowed to vote, even though polling places would officially close by then.
Voters in the largest city, Lagos, cheered when election officials arrived at a polling station in the suburb of Lekki nearly four hours after polls officially closed.
There have also been reports of violence and theft of ballot boxes in Lagos.
While some voters were angry about the delays, others patiently waited to vote.
“As a Nigerian you expect every eventuality, so I came out with my power bank and a bottle of water. I’m waiting for them to arrive so I can vote,” Edith, who voted for the first time, told the BBC.
Mr Yakubu said gunmen attacked some polling stations in southern Delta state and northern Katsina state, where voter card verification machines had been taken away.
They were subsequently replaced and security increased to allow for voting, he added.
But at 141 polling stations in the oil-rich southern state of Bayelsa, voting has been postponed until Sunday due to disruptions.
In the northeastern state of Borno, Mr Yakubu said militant Islamists had opened fire on election officials from a mountaintop in the Gwoza area, injuring a number of officials.
The run-up to the polls was overshadowed by a cash shortage caused by a failed attempt to redesign the currency, leading to widespread chaos at banks and ATMs as desperate people sought access to their money.
The new banknotes were introduced to deal with inflation, and also to buy votes. On the eve of the election, a member of the House of Representatives was arrested with nearly $500,000 (£419,000) in cash and a list of people to give it to, police say.
Whoever wins will have to deal with the currency redesign, a crumbling economy, high youth unemployment and widespread insecurity that killed 10,000 last year.
Voters also cast ballots for 109 federal senators and 360 members of the House of Representatives, with another vote for state governors in March.
The election has seen huge interest from young people – a third of eligible voters are under 35 years old.
Obi, 61, hopes to break Nigeria’s two-party system after joining the Labor Party last May.
Although he was in the PDP before then, he is seen as a relatively fresh face and enjoys staunch support among some segments of Nigerian youth, especially in the south.
The wealthy businessman served as governor of the southeastern state of Anambra from 2006 to 2014. His backers, known as the “OBIDients”, say he is the only candidate with integrity, but his critics argue that a vote for him is wasted as he is unlikely to win.
Instead, the PDP, which ruled until 2015, wants Nigerians to vote for 76-year-old Abubakar, the only major candidate from the country’s predominantly Muslim north.
He has run for president five times before – all of which he has lost. He is dogged by allegations of corruption and favouritism, which he denies.
He has spent most of his career in the corridors of power, serving as a top government official, vice president and a prominent businessman.
Most people view the election as a referendum on the APC, which has seen a period of economic hardship and growing insecurity.
The candidate, 70-year-old Tinubu, is credited with building Lagos, Nigeria’s commercial hub, during his two terms as governor until 2007.
He is known as a political godfather in the southwestern region where he wields enormous influence, but like Abubakar, he is also dogged by allegations of corruption over the years and ill health, both of which he denies.
A candidate must receive the most votes and 25% of the votes cast in two-thirds of Nigeria’s 36 states to be declared the winner.
Otherwise, a second round will follow in 21 days – a first in Nigerian history.
* Additional reporting from BBC teams across the country.