Violence and delays have marred presidential and parliamentary elections in Nigeria, where for the first time since independence in 1960, one civilian head of state is due to hand over to an elected successor.
BBC reporters across the country are sending their observations.
Bala Ibrahim: Kano city, Kano State : 21 April, 1645 GMT
Counting of votes is going on, some polling centres have announced the results and are getting ready to take the boxes to the electoral commission.
People have complained that elections started late in most areas but closed without extending the time.
Some polling centres experienced a shortage of election materials. It is calm now but there is a fear that tension may rise when the full results come out.
I have just got off the phone to a colleague in neighbouring Jigawa State who confirmed a report that thugs snatched ballot boxes from a polling station - right in front the area's traditional rulers.
And the electoral commission says its office in Ringim, Jigawa, was set ablaze.
Ado Saleh Kankia: Kaduna city, Kaduna State : 21 April, 1615 GMT
There has been electoral chaos in Kaduna where shambolic organisation has left voters angry.
Not many people in Kaduna had an opportunity to vote
The late arrival of voting material has meant some areas did not vote at all.
At one voting centre, the material turned up one hour before the polls were due to close. Party agents then decided the vote should be held on another day.
As police were taking the ballot papers away, people who had been waiting to vote started shouting and throwing stones at them.
The police fired teargas to scatter the crowd.
Other polling stations found they were short of presidential ballots - sometimes only having 150-200 - when their allocation was 500.
Controversially, many of the presidential ballots in Kaduna had no serial numbers - the ones I saw only had zeros on them.
Meanwhile, the senate votes in north and central Kaduna have been postponed indefinitely - without an explanation from electoral officials.
Hassan Sahabi Sanyinnawal: Sokoto city, Sokoto State: 21 April, 1545 GMT
I have just arrived at Magajin Gari polling station where voting has closed and election officials are now counting the votes before the official time for the polls to close.
People are waiting to know the result.
Voters at the polling station near government house have also finished casting their votes.
Election officials there are waiting for the official closing time at 1600 GMT to start counting.
Most voters left polling stations unhappy, saying they do not expect a fair result from the electoral body.
Security is still tight. Youths have now turned some streets into football pitches.
Mansur Liman: Katsina city, Katsina State : 21 April, 1539 GMT
There have been allegations that ballot boxes have been snatched in the city.
My colleague visited nine polling stations where voters described men running in and taking the boxes; the electoral commission has refused to comment on the issue.
At a voting centre I visited, the ballot boxes were also missing.
A visibly angry woman told me that she had been holding on to her ballot paper for four months and now she was at the polling booth there was no opportunity to use it.
However, a ruling People's Democratic Party (PDP) official has told me the story of the snatchings is not true.
A relaxed-looking Umaru Yar'Adua, the PDP's presidential candidate, voted at around midday at Ladoji primary school where voting had started on the dot at 1000 local (0900 GMT).
Voting is still continuing, but turnout has been low.
Chris Ewokor: Warri, Delta State : 21 April, 1452 GMT
Voting has been peaceful in this oil-rich port town even though it started three hours behind schedule.
Turnout is low with some polling stations having less than 50 voters. It is much less rowdy than last week's state vote.
The tension has been defused as the security forces are not being as heavy handed and there are fewer of them - the market and some shops have been open and people have been to go about their business.
Young boys took advantage of the traffic-free roads to play football on the highways - using tins as goal posts.
The protesting women, who allege last week's election was rigged, did not take to the streets today because of the security presence.
They chose to shun the election by staying at home.
Other no-shows complained that they were not able to vote last week, so they were not going to bother this time.
A heavy downpour of rain is forcing late voters to flee polling stations.
Yusuf Sarki Muhammad: Enugu city, Enugu State : 21 April, 1425 GMT
The voting material has eventually arrived in Enugu - to the visible relief of Senate President Ken Nnamani, who I was with when he heard.
However some polling stations only became operational as late as 1440 local time (1340 GMT).
Turnout at Achra Layout voting centre is large, and people are worried they won't get a chance to cast their ballot before 1700 local time (1600 GMT) when the polls close.
One lady told me she was voting for good roads and electricity.
Another voter - angry that he wasn't on the voter register for last week's state elections - was lining up again hoping to find his name on the list for the national vote.
"If it's not there I will have been killed by the ballot box. My citizenship will be useless," he told me.
All the hustle and bustle - the traffic, car horns, cursing and swearing - is missing from the city's streets.
Some food sellers and small side-street green grocers are open for business though.
Fidelis Mbah: Lagos : 21 April, 1338 GMT
Voting is still going on, although turnout is still low.
Many people have stayed indoors because they seem aggrieved about last week's state election result.
The restriction on movement has also meant some people haven't been able to get to polling stations.
The youths, however, turned out in force to play football. All the major highways were turned into football pitches for most of the morning until midday when the heat forced them to retire.
Governor Bola Tinubu has condemned the cancellation of many of the ballots in the state.
Elections for some senatorial and house of representative seats had to be cancelled because the ballot papers were missing some party symbols.
He said it was a plot by the government to rig the vote in favour of the ruling party.
Will Ross: Kubwa, Abuja : 21 April, 1213 GMT
Voters lining up under the tree here have found themselves in the middle of an impromptu basketball court as young children have nailed a toilet seat half way up the tree to use as a hoop.
There are about 100 people in the queue which is moving slowly.
Talking to people, many say they are determined to make their vote, but fear what might happen behind the scenes.
Observers have popped in here and party agents are sitting next to the polling booth.
Ado Saleh Kankia: Kaduna city, Kaduna State : 21 April, 1145 GMT
Voting has not started at most polling centres in the Tudun Wada and Rigasa areas of the city.
It is a bright day and people are getting impatient.
The large crowds of people gathered around some of these polling centres insist that they must cast their votes.
Election officials have been seen mingling with them.
Peter Okwoche: Yenagoa, Bayelsa State : 21 April, 1145 GMT
Voting has just started here and the atmosphere is fairly laid back given the gun battle last night between militants and security forces.
This morning Goodluck Jonathan, the state governor and running mate to the ruling party's candidate, made a state-wide address urging people to vote en masse.
There is heavy security around government house, where he lives. Anyone approaching the area has to put their hands up in the air in surrender.
A hotel was badly burned in last night's attack.
I've just been down to the waterfront, where the militants entered the city and there are loads of spent shells lying on the floor and several buildings were dynamited in the fighting.
I met one soldier who was wounded in the leg during the battle. He said at least one militant was killed.
No-one knows why they attacked and unconfirmed reports say three people died.
Shehu Saulawa: Bauchi city, Bauchi State : 21 April, 1127 GMT
Voting has still not yet commenced.
People were getting impatient, but election materials have just started to be distributed to the various polling centres.
Fidelis Mbah: Lagos : 21 April, 1126 GMT
In Lagos state, the election for two senatorial seats and seven house of representative seats in the national assembly have been cancelled as some party logos were missing from the ballot papers.
People don't seem to be angry, but are asking questions to which they are not getting answers.
I had to go to the electoral commission headquarters to find out what was going on.
Otherwise, voter turnout is generally low across Nigeria's commercial capital.
Dan Isaacs: Abeokuta, Ogun State : 21 April, 1107 GMT
President Olusegun Obasanjo voted just a few minutes ago.
Although presidential ballot papers have arrived in this state, no papers have turned up for the senatorial ballot, so that has been cancelled.
The scene is calm and the town has virtually closed down.
After he had voted, Mr Obasanjo spoke of the attempts to disrupt the poll in the last 24 hours.
He described last night's violence in southern oil-rich Bayelsa State as an attempt on the life of the ruling party's vice-presidential candidate Goodluck Jonathan.
But he said nothing would deter Nigerians from voting.
Alex Last: Daura, Katsina State : 21 April, 1102 GMT
Not long ago youths, furious that only half the ballot papers had arrived in this area torched some shacks close to the headquarters of the electoral commission.
This is opposition candidate Muhammadu Buhari's home town.
He actually went out to calm the people and then travelled to vote in a small mud and tin hut near his father's old house, surrounded by a jubilant crowd of supporters.
The town is now quiet.
Senan Murray: Abuja : 21 April, 1057 GMT
Voting has just started at Garki II polling station in the centre of the capital city.
There is an orderly horseshoe queue. One voter, Solomon, said he was happy at how things were progressing except for the sun, which is scorching.
The recently reprinted presidential ballot papers have party symbols on them - no names or photos of the candidates.
Bala Ibrahim: Panshekara, Kano State : April 21, 1050GMT
This is where the Nigerian army and Islamists clashes earlier this week.
But it does not seem to have affected the election, with some people turning up as early as 0800 local time (0700 GMT) to queue.
Voting has started - although this polling station at Panshekara primary school on the outskirts of Kano city opened late.
And while security is tight with security men conducting stop and searches on motorists following the recent crisis there is a large turnout.
Yusuf Sarki Muhammad: Enugu city, Enugu State : 21 April, 1017 GMT
Voting has not started in Nigeria's coal capital, which has fallen on hard times because of the south's oil wealth.
Voting materials have been slow to arrive
The state's electoral commissioner is waiting at the airport for the election material to arrive from Abuja.
It is hot - the sun is so bright, you can't look at it directly and the city is quiet.
Movement is restricted because of the high number of armed forces and roadblocks.
I have just seen former rebel leader Chukwuemeka Odumegwu-Ojukwu leave the city to go to his village Nnewi to vote.
He is the most respected Igbo politicians and is the presidential candidate for the All Progressive Grand Alliance.
Senan Murray: Abuja : 21 April, 1017 GMT
I have been to four polling stations in the capital and voting has not started at them, although electoral officials are beginning to arrive.
People are out and about now, most chatting and relaxing while they wait for voting to get under way.
At some stations queues have formed and people are being given numbers so there is no confusion when voting begins.
Alex Last: Katsina State : 21 April, 1006 GMT
I am outside the station where Muhammadu Buhari - the opposition candidate for the All Nigeria People's Party - is due to cast his vote.
Ballot papers and boxes have arrived, but only half the amount needed.
Will Ross: Kubwa, Abuja : 21 April, 1008 GMT
Voting began at this polling station in the outskirts of the capital about half an hour ago.
There is a long queue, perhaps a couple of hundred people, lining up under a tree.
It is not moving fast and does not seem well organised.
Ahmed Idris: Yola, Adamawa State : 21 April, 0938 GMT
I am standing at Ajiyah polling station in the centre of the city.
Election materials have just been offloaded from the vehicles.
Large crowds of voters have gathered, possibly because this is where Nigeria's Vice-President Atiku Abubakar - the president for the opposition Action Congress - is going to cast his vote.
Peter Okwoche: Yenagoa, Bayelsa State : 21 April, 0926 GMT
We've just arrived in the city where there was a shootout yesterday between militants and security forces.
Voting has not started here and there are not many people in the streets.
Police are thoroughly searching all vehicles.
Shehu Saulawa: Bauchi city, Bauchi State : 21 April, 0917 GMT
Election materials have not arrived at Aminu Street polling station in the town centre, but election officials are waiting as voters gather to cast their votes.
Chris Ewokor: Warri, Delta State : 21 April, 0909 GMT
It's bright and sunny here, but the streets are empty and no voters are out.
The town is tense because women have been protesting over the last four days about last week's governorship election, alleging it was rigged in favour of the People's Democratic Party.
They say they will not come out to vote today unless last week's results are cancelled.
Detachments of security agents are station at strategic locations around the town.
Hassan Sahabi Sanyinnawal: Sokoto city, Sokoto State: 21 April, 0907 GMT
Only one election official has arrived here at Gawon Noma polling station near the electoral commission headquarters, but there are no election materials. A few voters are gathered waiting outside anxiously.
Fidelis Mbah: Lagos : 21 April, 0847 GMT
There's no sign that voting will start as scheduled here in about 10 minutes.
I have just been around the city and there are a couple of voters hanging around some polling stations, but there are no sign of electoral officials or voting material.
There are soldiers everywhere.
Ado Saleh Kankia: Kaduna city, Kaduna State : 21 April, 0837 GMT
Voting is due to start in 20 minutes, and some voters have started visiting polling stations in city.
Election officials have been seen at some polling stations waiting for the arrival of election material from the electoral commission.
Security is tight. The streets are deserted except for official vehicles and some motor bikes.
Senan Murray: Abuja : 21 April, 0750 GMT
It is bright and sunny in the capital city - the heat is yet to hit us.
Voting got under way in Abuja about two hours late
The attempt to blow up the Independent National Electoral Commission (Inec) with a tanker, which would usually be big news on morning TV talk shows, is overshadowed by polling day preparations.
Curiously, it's not even the subject of discussion for the few people at work. A group of guards and cleaners I have just met did not seem worried about it.
Musa, in his twenties, said it was "not important" as he believed it was stage-managed to win support for Inec, seen as being sympathetic to the ruling People's Democratic Party.
Otherwise, the city is fairly empty and the roads on my way into work were deserted except for a few joggers and policemen on the highways of the capital.
There was not a single taxi to be had - I was walking, when luckily a man stopped to give me a lift.
He was rushing back from hospital where he had just dropped off his brother, anxious to get home before the no movement order comes into affect at 1000 local time (0900 GMT ) when the polls open.
Transport is not the only issue for bachelors like me today. All the restaurants are closed - it will be a day of starvation.
Fidelis Mbah: Lagos : 21 April, 0636 GMT
Stop and search sums up the situation in Lagos. Police patrol vans are on the streets of Nigeria's commercial capital and security men are out in force.
Otherwise the roads are deserted of people, which is not unexpected as they possibly fear harassment from the security forces.
A few commercial vehicles are out hoping to do some business before the no movement order comes into force an hour before the polls open at 1000 local time (0900 GMT).
Voting materials were being distributed in the state last night.
People here are more concerned with the national assembly elections as they know that presidential power is moving to the north.
They want to make sure there are people at a national level who will represent their interests.
Mansur Liman: Katsina city, Katsina State : 21 April, 0618 GMT
Security is tight. The streets are deserted except for one or two motor bikes that are going. There are a lot of military roadblocks with men in full combat gear.
The presidential ballot papers arrived overnight and the electoral commission says they have already been distributed to other parts of the state.
No voters are out yet - word seems to have spread that the polling has been delayed by two hours.
Peter Okwoche: Port Harcourt, Rivers State : 21 April, 0610 GMT
It is a bright morning, the sun is really high in the sky. I am standing right in front of the Independent National Electoral Commission (Inec) office in Nigeria's main oil city.
It is madly busy here with cars and trucks being loaded with voting material and a heavy police and military presence.
The ballot papers arrived late last night and many are sceptical that they will be able to be distributed to polling stations in time given the creeks of Rivers State.
But the Inec state commissioner told me firmly, "Elections will start at 1000."
Sola Odunfa: Abeokuta, Ogun State : 20 April, 1956 GMT
I arrived in President Olusegun Obasanjo's home town this evening - and everyone is talking about the election.
To them it is something special as they are proud to have had a head of state for eight years.
From the posters and billboards along the highway leading to the town, you see only the president and local ruling party politicians smiling down at you.
There is room only for the PDP (People's Democratic Party) here.
After I checked into my hotel, I took a drive around the town; however, I could see nothing as there was a blackout.
It appears even the president's home is subject to electricity cuts.
Mansur Liman: Katsina city, Katsina State : 20 April, 1745 GMT
It is shocking to see that there is little enthusiasm for the election in the home state of two main presidential candidates: Umaru Yar'Adua (of the ruling People's Democratic Party) and Muhammadu Buhari (of the opposition All Nigeria People's Party).
60m registered voters
120,000 ballot boxes
360 House of Representative seats to be elected
109 Senate seats to be elected
24 presidential candidates
Main contenders: Atiku Abubakar for the AC, 60-years-oldMuhammadu Buhari, ANPP, 64Umaru Musa Yar'Adua, PDP, 55
Polls open 1000-1700 (local time) (0900-1600 GMT)
To avoid a run-off, a candidate needs highest number of votes overall and at least 25% of votes in 24 of the 36 states
News of the ballot papers delay and the postponement of polling for two hours tomorrow has not helped matters.
Mr Buhari seems to enjoy more support on the ground, although the city boasts more PDP posters.
The general view is that Mr Yar'Adua did well as governor, particularly in the city, but his association with President Olusegun Obasanjo has affected him negatively.
The city is busy and businesses are open as normal.
Earlier on I passed through many military roadblocks set up around town.
Bilkisu Labaran Ohyoma: Abuja : 20 April, 1706 GMT
Campaigning has stopped, but Nigerians - being their usual ingenious selves - have been sending last minute text messages canvassing for votes for their candidates in exchange for free mobile phone air time.
Right now I am at the headquarters of Independent National Electoral Commission (Inec) in the centre of Abuja where it is all happening this afternoon.
Inec chairman Maurice Iwu gave a press conference earlier in which he assured Nigerians and the world that the electoral commission was fully ready to conduct tomorrow's elections.
And you do get that sense here: it is a beehive of frantic activities.
People and journalists are coming and going and there is a constant stream of vehicles.
Security is tight, but not unduly so.