Photos: Millions head to polls as Nigeria elects new president

Onitsha: Nigerians were voting on Saturday to elect a successor to President Muhammadu Buhari, with many hoping the next leader will steer Africa's most populous nation and biggest economy on a new course after years of worsening violence and hardship. Polling stations were scheduled to open at 8.30am, though reporters at locations across the country saw a mixed picture, with delays of several hours in some places while voting got underway more swiftly at others.

Several election officials said they had been delayed by the late arrival of vehicles to transport them and the election materials.

In the northeastern city of Maiduguri, the vice presidential candidate from the ruling party, Kashim Shettima, arrived to cast his ballot but was unable to do so as his designated polling station had not opened. In another northeastern city, Yola, opposition presidential candidate Atiku Abubakar was able to vote, surrounded by a chaotic scrum of media and supporters.

In the southeastern city of Onitsha, large numbers of voters waited for election officials to turn up. Buhari, a retired army general, is stepping down after serving the maximum eight years allowed by the constitution but failing to deliver on his pledge to bring back order and security across Nigeria, Africa's top oil-producing nation.

The two parties that have alternated in power since the end of army rule in 1999 are facing an unusually strong challenge from a minor party candidate, who polls suggest has a chance thanks to support from young voters. With seats in the National Assembly also up for grabs, more than 93 million people are registered to vote at some 176,600 polling stations that were supposed to be open between 8.30am and 2.30pm.

Vote-counting will begin as soon as polls close and results will be posted outside polling stations, according to the Independent National Election Commission (INEC). The final tally from the 36 states and federal capital Abuja is expected within five days of voting.

The run-up to the vote was marred by violence, a pattern seen in previous Nigerian elections, with the killing of a senatorial candidate in the volatile southeast region on Wednesday the latest in a series of serious incidents. The election comes as Nigerians are struggling to cope with a shortage of cash caused by a botched plan to swap old bank notes for new ones that has wreaked havoc on people's daily lives and led to scenes of violence at banks and cash machines.

The new president will also have to grapple with problems ranging from high inflation, deep poverty and energy shortages, to industrial-scale oil theft in the south and rampant crime everywhere. For the election, land borders were closed, soldiers were patrolling the streets in several states and movements were restricted in an effort by the authorities to boost security.

The main contenders in the race to succeed Buhari are former Lagos governor Bola Tinubu (above), 70, of the ruling All Progressives Congress, former vice president Atiku Abubakar, 76, of the main opposition Peoples Democratic Party, and former Anambra State governor Peter Obi, 61, of the smaller Labour Party.

Tinubu and Atiku (above), as he is known in Nigeria, are both political heavyweights with decades of networking behind them and bulging campaign coffers. Both Muslims, Tinubu is an ethnic Yoruba from the southwest and Atiku is a Fulani from the northeast.

Obi (above), a Christian from the Igbo ethnic group, has less of a political machine behind him but has used a slick social media campaign to generate huge enthusiasm among young voters, with some even calling themselves the "Obidients". " We have come out to vote. Our son Peter Obi is in the race and we cannot be found wanting," said Maria Onyeke, who was waiting for her polling station to open in Onitsha, a predominantly Igbo city.

Nigeria has a long history of electoral fraud and violence, though its polls have been getting gradually cleaner in recent cycles. INEC says it has introduced new technology and procedures to ensure a free and fair election, such as a Bimodal Voter Accreditation System (BVAS) that identifies voters using biometric data.

Reuters reporters in several locations said INEC officials were struggling to get the BVAS devices to work because of poor network connectivity. Despite INEC's precautions, analysts have warned there were still risks that cash-strapped citizens could be vulnerable to vote-buying attempts by candidates, and a shortage of fuel that could make it hard for INEC to deploy staff and equipment to all areas.

Nigerian President Muhammadu Buhari and his wife Aisha Buhari arrive to cast their votes.

An Independent National Electoral Commission (INEC) official uses a Bimodal Voter Accreditation System (BVAS) to check the details of a voter at a polling station in Maiduguri.

Voters queue to write their names on a unofficial voters list while waiting for the late election material to arrive at a polling station in Abuja.