Q&A: Nigeria elections
Unrest in Nigeria erupted following presidential elections on Saturday 16 April, a week after delayed legislative polls were finally held.
What happened in the presidential elections?
Goodluck Jonathan from the governing People's Democratic Party (PDP) was declared the winner with 57% of the vote, taking 22.5 million votes.
The runner-up, General Muhammadu Buhari, of the Congress for Progressive Change (CPC), took 12.2 million votes.
International observers said polling was generally free and fair and there has been praise for the Independent National Electoral Commission.
The African Union observer team said it was Nigeria's best poll for decades, but this did not stop riots breaking out in many northern cities, where Gen Buhari is popular.
To win in the first round, a candidate needs at least 25% of the vote in two-thirds of Nigeria's 36 states, as well as a majority of the total votes cast.
The protesters accuse PDP politicians in the north of rigging to allow Mr Jonathan to reach this threshold.
They also claim there are discrepancies between turnout and results in some areas of the south, Mr Jonathan's powerbase.
Do the protesters have a point?
Nobody is saying the vote was perfect - there were problems in some areas, however, nothing comparable to the rigging and intimidation seen in 2003 and 2007.
The main problem for the opposition was that they failed to unite behind a single candidate.
They had hoped the vote would go to a second round.
But the Action Congress of Nigeria candidate, former anti-corruption boss Nuhu Ribadu, did not do well in the party's powerbase in the south-west.
He is a Muslim from the north-east, and in the end his supporters chose loyalty to a southern candidate over party.
Is there always a north-south divide to politics?
Elections in Nigeria tend to be about ethnicity, religion and regionalism, not issues.
But it is the first time in Nigeria's recent history that the presidential election result has exposed the huge division between the mainly Muslim, Hausa-speaking north and Christian and animist south.
Often the winning candidate - irrespective of region, religion or ethnicity - has commanded a wide national spread in the first round.
Historically, this was due either to a formal alliance by political parties or - more recently - an informal agreement within the governing PDP party to alternate the presidency between the north and the south after two terms in office.
However, this rotation was broken when Mr Jonathan succeeded to the presidency last year after the death of Umaru Yar'Adua, a northerner. PDP powerbrokers wanted their candidate in this election to be a northerner.
And much of the anger being expressed by the young men rioting in northern cities comes down to frustration.
The north is far behind the south in terms of development, education and job opportunities - some of the issues politicians have often promised to address and failed to deliver.
What have been the main campaign issues?
Security, corruption and electricity.
Since the country returned to democracy in 1999, it has been bedevilled by occasional outbreaks of deadly violence between the numerous ethnic groups who make up this nation of 160 million people.
The oil-producing Niger Delta has experienced continuous unrest due to the activities of militants who say they want local people to keep more of the region's oil wealth.
Around the central city of Jos, groups divide along ethnic, religious, political and economic lines. They frequently clash and hundreds have already been killed this year.
In the north-east, the radical Boko Haram Muslim sect, which says that Western education is forbidden, has battled the security forces resulting in deaths and fear in the city of Maiduguri.
Black-outs are a common experience in Nigeria - an annoyance at home and a massive brake on economic growth. Despite spending $16bn (£10bn) in the last 12 years in order to improve supply, it can only produce 4,000 megawatts of electricity, compared to the 100,000 MW it says it needs to be an industrialised country.
This brings us to the next issue, corruption.
Despite being the sixth largest producer of oil in the world, and selling about two million barrels of oil per day, there is very little to show for it in terms of development.
The majority of Nigerians still live below the poverty line and infrastructural development seems almost non-existent.
So President Jonathan faces huge challenges on a number of fronts as well as healing the regional divide.
Who were the main presidential candidates?
Of the 20 candidates, only four had any chance of winning.
President Goodluck Jonathan of the ruling People's Democratic Party became president in May 2010 after the death of his predecessor, Umaru Musa Yar'Adua.
Former military ruler Muhammadu Buhari of the Congress for Progressive Change contested both the 2003 and 2007 elections. He lost to the PDP candidate in elections that were heavily criticised by the international community.
Nuhu Ribadu, the former head of the Economic and Financial Crimes Commission, contesting for the Action Congress of Nigeria, the largest opposition party in the country.
The fourth main candidate was Ibrahim Shekarau of the All Nigeria Peoples Party, the current governor of Kano State.
Are the other elections important?
After the presidential poll, the most important election is for the 36 state governors, who enjoy wide powers - and huge budgets. (In some case, they control more money than the leaders of neighbouring countries.)
Even the president has to bow to their pressure because they control the delegates of their states in primary elections, and they are the chief security officers of their respective states which gives them authority over the police.
When the electoral commission is short of funds, the governors normally come to its aid in their states, something that is seen as another way of bribing election officials.
The election for the governors is set for 26 April, although this has been postponed by two days in two of the states worst affected by the violence - Kaduna and Bauchi.
What happened in the legislative elections?
They were due to be held on 2 April but were delayed at the last minute because election materials had not been delivered in many parts of the country.
Many people feared the delay was part of an elaborate plan to rig the polls but most observers say they passed off relatively smoothly.
The governing People's Democratic Party (PDP) seems to have lost ground and several party leaders lost their seats but it remains the biggest party in the National Assembly.
And despite the initial chaos, observers said it was reasonably free and fair.
To win at the first round, a candidate not only needs the majority of votes cast, but at least 25% of the vote in two-thirds of Nigeria's 36 states. Goodluck Jonathan, of the PDP, reached that threshold in 31 states; runner-up Muhammadu Buhari of the CPC only did so in 16 states.
Nigeria's 160 million people are divided between numerous ethno-linguistic groups and also along religious lines. Broadly, the Hausa-Fulani people based in the north are mostly Muslims. The Yorubas of the south-west are divided between Muslims and Christians, while the Igbos of the south-east and neighbouring groups are mostly Christian or animist. The Middle Belt is home to hundreds of groups with different beliefs, and around Jos there are frequent clashes between Hausa-speaking Muslims and Christian members of the Berom community.
Despite its vast resources, Nigeria ranks among the most unequal countries in the world, according to the UN. The poverty in the north is in stark contrast to the more developed southern states. While in the oil-rich south-east, the residents of Delta and Akwa Ibom complain that all the wealth they generate flows up the pipeline to Abuja and Lagos.
Southern residents tend to have better access to healthcare, as reflected by the greater uptake of vaccines for polio, tuberculosis, tetanus and diphtheria. Some northern groups have in the past boycotted immunisation programmes, saying they are a Western plot to make Muslim women infertile. This led to a recurrence of polio, but the vaccinations have now resumed.
Female literacy is seen as the key to raising living standards for the next generation. For example, a newborn child is far likelier to survive if its mother is well-educated. In Nigeria we see a stark contrast between the mainly Muslim north and the Christian and animist south. In some northern states less than 5% of women can read and write, whereas in some Igbo areas more than 90% are literate.
Nigeria is Africa's biggest oil producer and among the biggest in the world but most of its people subsist on less than $2 a day. The oil is produced in the south-east and some militant groups there want to keep a greater share of the wealth which comes from under their feet. Attacks by militants on oil installations led to a sharp fall in Nigeria's output during the last decade. But in 2010, a government amnesty led thousands of fighters to lay down their weapons.