President Muhammadu Buhari and his main challenger, businessman Atiku Abubakar, cast their ballots in Nigeria's presidential election on Saturday as voting began after a week's delay in Africa's biggest economic power.
Analysts say the vote is too close to call, with the outcome set to hinge on which man voters most trust to revamp an economy still struggling to recover from a 2016 recession.
Buhari, a former military ruler who was later elected president, is seeking a second term in charge of Africa's most populous nation and top crude producer. Atiku, a former vice president, has pledged to expand the role of the private sector.
The two candidates lead a field of more than 70 challengers. Reuters witnesses observed some delays to the opening of polling stations and problems with voting systems in the early part of the ballot.
Last Saturday, the election was postponed around five hours before polling stations were due to open by electoral commission, which cited logistical factors.
Buhari, who voted in his hometown of Daura in the northern state of Katsina, said: "I will congratulate myself, I'm going to be the winner" when asked by reporters if he would congratulate his rival, should Atiku win the election. Atiku later cast his ballot in the eastern Adamawa state.
"I look forward to a successful transition," he told reporters shortly after voting.
Nigerians queued at polling booths around the country where voting officially began at 8:00 a.m. local time (0700 GMT) and is due to close at 2:00 p.m.
However, several polling stations across the country were slow to open and others reported problems with machines meant to verify voters cards, Reuters witnesses said. The country has 72.8 million eligible voters.
"I've been to 10 polling units today. I've been redirected many times," said Victor Kanoba a voter in Lagos.
John Tomaszewski, an observer with the joint U.S. National Democratic Institute and International Republican Institute delegation, said delays had been somewhat expected given the logistical challenge of getting materials to the polling stations in time for opening.
"This will be something to watch throughout the day," he said. "Logistics weren't properly managed despite the postponement of the polls," said Idayat Hassan, director of Abuja-based think tank Centre for Democracy and Development, which is also observing the election.
In the capital Abuja, Chukwunwike Ogbuani, a lawyer, said he was worried by the delays.
"This polling booth they say has about 20,000 registered voters... if there is at least up to 50 to 60 percent turnout it will be difficult to finish in a day. I don't see everybody that is here voting within the stipulated time."
In Lagos' business district of Victoria Island, Reginald Anthony, 45, who runs a transport business, said: "We are seeing a transparent election, everything is open for everyone to see".