Some polling stations closed on schedule at 13:00 GMT
Other stations will stay open if there are queues
Polling stations that opened late or were disrupted are still open
Isolated incidents of violence
Voters attacked with axe in Lagos
Ballot boxes smashed at polling station in Lagos
Gunfire heard in Maiduguri before voting began
Yobe voters miss poll to hide from militants
President Muhammadu Buhari, 76, is running for a second term (party APC)
His main challenger is Atiku Abubakar, 72, a former vice-president (party PDP)
In total there are 73 registered presidential candidates
51% of the electorate is under the age of 35
Nationwide there are 120,000 polling stations
About 73 million people can vote for president and MPs
A woman has been stabbed at a polling station in the south-west of Nigeria over what is believed to have been an argument about who was due to vote next.
BBC Yoruba's Samson Owolabi reports that the incident took place at the Ife Central polling station, in Osun state.
A woman has been arrested and taken away by the police.
As well as providing live coverage of the election in English, the BBC also has live pages in other languages that are spoken in Nigeria.
Some of Nigeria's top stars have been using their social media accounts to urge people to take part in today's poll.
2Baba, or Innocent Idibia, who has nearly four million followers on Instagram, has shared a picture of the mark on his thumb to show that he has voted:
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Davido, arguably the country's biggest music star, has also told his 4.5 million Twitter followers to get involved today:
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And DJ Cuppy has also joined the voters' queue.
She's posted a video of her and her dad and tells people to "go and vote and let's shape the future of Nigeria".
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Nigeria has a very young population and more than half of the electorate is under the age of 35.
Vice presidential candidate Peter Obi has told the BBC that he found the voting process "clumsy".
He was speaking to BBC Igbo's Chioma Obianinwa in Anambra state just after he voted in Amatutu village.
"The process is a bit clumsy, it wasn't as smooth as I expected it to be. It took a while for us to go through the process," he said.
"I hope and pray that it all goes well," he added.
PDP Vice-President candidate Mr Obi is the running mate of Atiku Abubakar who is one of the two main contenders for president.
The main challenger to President Muhammadu Buhari has cast his vote.
Atiku Abubakar, who represents the opposition People's Democratic Party, was mobbed by reporters after voting at his polling station in Adamawa state, in the north-east of the country.
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In his tweet you can't hear what he's saying, but in his message he does urge other Nigerians to go out and vote.
Just under 74 million Nigerians have a voter's card, but there have been concerns that turnout could be affected by the one-week delay in the poll.
Residents in the village of Geidam in Yobe State in north-east Nigeria say they have fled an attack by suspected militants so are unable to go to vote.
"We have along with our wives and children and hundreds of others fled. We are right now running and hiding in the bushes," a Geidam resident, Ibrahim Gobi, told Reuters news agency.
The BBC's Kaura Abubakar was told by a Geidam resident that officials said voting in the town would begin at 11am, but it appeared that most residents had fled.
A Nigerian army spokesman insisted that the military repelled the attack and people have turned out to vote.
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The spokesman posted the tweet on a thread about another report of gunfire.
He said that the gunfire heard in Maiduguri, the capital of Borno State, the state next to Yobe, was just for security purposes and was not targeted at members of the public.
BBC Pidgin reporter Olubunmi Okunnu in Lagos, Nigeria's commercial hub, is at a polling station in Ikeja and has taken pictures of things going smoothly there.
Voters can be seen getting their thumb print checked to help identify them.
People have also been checking on the voter lists that have been posted to see if their names are there.
The week-long delay of the Nigerian election was used by some commentators as another example of a problem with democracy in Africa.
But some have gone even further to question whether certain African countries should scrap democracy altogether.
Malian music legend Salif Keita has, however, given up on democracy. He recently suggested that the continent needs a "benevolent dictator like China".
"To have a democracy, people have to understand democracy, and how can people understand when 85% of the people in the country cannot read or write," he asks.
Others have argued that many African countries don't have a democracy in reality any way.
Only nine countries out of the 54 in Africa were categorized as "free" by the 2019 Freedom House report, external, the same number as a decade ago.
Read More in Dickens' Olewe's analysis on the BBC News website.
The BBC's Ayo Bello is at a polling station in Adamawa state, north-east Nigeria.
There are long queues but things appear to be going smoothly.
Former President Goodluck Jonathan has voted in Bayelsa state in the south-east of the country, reports BBC Pidgin's Andrew Gift.
Afterwards, he wouldn't say who he voted for and told reporters that his comments could be interpreted as campaigning.
Mr Jonathan ran in the last election in 2015 but lost to Muhammadu Buhari.
His willingness to concede defeat was seen as an act of statesmanship at the time.
The BBC's Dooshima Abu is reporting that voting materials arrived late at the polling station where she is, in Makurdi, the capital of Benue state in Nigeria's Middle Belt.
This has meant a delay in the voting process.
She says that many voters came at 06:00 (05:00 GMT) - two hours before polls opened - to start queuing.
Some expressed their displeasure at having to wait, but told our reporter that they would wait in the scorching sun to make sure they cast their vote.
Chris Ewokor
BBC Africa, Abuja
Voters' patience has been tested at one polling station in the Abuja suburb Dutse Alhaji.
An hour after the polls were meant to open, people were still queuing to vote.
Workers at the LEA primary school were not clear what they were meant to do or even if they had the right voting materials.
There was also confusion as some people could not find their names on the list displayed on the wall.
Polls are due to close at 14:00 (13:00 GMT) but the electoral commission says that anyone still in the queue when the polls shut will be able to vote.
Our BBC Pidgin reporter Onyinye Chime has been catching up with one voter Amuda Basil in Edo state, in the south of Nigeria:
He told her that he isn't voting for himself but for his children's future.
The two main contenders for president, Muhammadu Buhari and Atiku Abubakar are both over 70 years old.
That's in contrast to the age of many of the voters - more than half of Nigeria's 84 million registered voters are under 35.
Overall, 40% of Nigeria's 196 million people are under the age of 14, the UN says.
The election is dominating discussions on Twitter in Nigeria according to figures from Trendsmap:
Image source, TrendsmapPeople are using the hashtags #NigeriaDecides2019, #VoteNotFight and #ElectionNotWar to share thoughts and images from the polling stations.
People are also posting pictures of their inked thumb or finger that they used to vote:
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For some the Nigerians who have been forced from their homes, polling stations have being set up in camps for internally displaced people, like this one:
Image source, Nura GandiThe camp is in Gandi Village in Sokoto state, in the far north-west of the country.
Our BBC Hausa reporter Usman Binji says around 500 people who have fled bandits in the area live in this camp.
BBC Focus on Africa's Peter Okwoche has been at a polling station in the capital, Abuja.
He took this short video of a woman casting her three votes and then giving a thumbs up.
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There are three elections happening today:
A photo of President Muhammadu Buhari casting his ballot shows that he has voted for his party.
This is the wide shot as captured by a photographer from the Reuters news agency:
Image source, ReutersBut zooming in you can clearly see his finger print next to the symbol for his All Progressives Congress party. This is the ballot paper for the House of Representatives.
Image source, ReutersVoters mark the ballot paper with a finger print, but it is important that the mark does not cross a line, which would invalidate the vote.
Party symbols rather than candidates' names are displayed.
There are 73 candidates running for president.
There are also elections for the two federal houses of parliament.
Our BBC Pidgin reporter in Kano state, Mansur Abubakar, reports that the roads are empty today as people either vote or stay at home.
That's something young boys are taking full advantage of by playing a game of football:
President votes in his home town
Ishaq Khalid
BBC Africa, Daura
President Muhammadu Buhari has voted at a polling station here in Daura in the far north of the country.
He said he was happy to vote.
I asked him whether he would accept the results and congratulate the winner if he loses, he responded: "I will congratulate myself" as he believes he is going to win.
Mr Buhari is facing 72 challengers but his main rival is Atiku Abubakar.
The independent electoral commission (Inec) has warned people not to sell their vote as they go to elect a new president and federal parliament.
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It has also advertised phone numbers to call if anyone notices any irregularities:
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