Nigerian election postponed again
Nigeria has postponed its parliamentary election until next Saturday - the second such delay in two days.
The vote was initially due to take place on Saturday, but staff and papers failed to materialise at polling stations around the country.
After first calling the election off until Monday, officials further delayed it until next weekend.
The election commission's decision means presidential and state elections have also been pushed back.
The BBC's Caroline Duffield in Lagos says the country's political culture of vote-rigging and violence has made it difficult for people to accept the official explanations for the delay.
She says many voters - and some politicians - think political interference caused Saturday's chaos.
The elections are seen as a vital test of Nigeria's democratic credentials.
Electoral chief Attahiru Jega was brought in last year to overhaul a system often regarded as flawed.
The electoral chaos has led some to question his suitability for the job.
Announcing the second delay, Mr Jega said the decision had the backing of all political parties.
"Requests to reschedule the national assembly elections have come from a cross section of stakeholders, including political parties and civil society organisations," he said.
"We are more determined now to ensure that the 2011 elections are free, fair and credible."
The People's Democratic Party (PDP) has won all three elections since the end of military rule in 1999, amid widespread claims of rigging and cheating.
Nigerian elections are also marked by violence - and security had been high in the run-up to Saturday's aborted poll.
But Amnesty International said at least 20 people had been killed in election-related violence over the last two weeks.
The voting process had already started on Saturday, with large turnouts reported in cities such as Lagos and Kano, before Mr Jega announced the initial postponement.
Some 73 million people have registered for the election, where they will vote for 360 seats in the House of Representatives, and 109 in the Senate. The PDP holds more than three-quarters of the seats in both houses.
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.