ABUJA, Nigeria (AP) — Frustrated Nigerians cast their ballots into the evening Saturday, hours after the official deadline for joining the voting line in Africa’s most populous nation after late starts and sporadic violence caused delays at polling stations.

Election officials blamed the delays on logistical issues, though other observers pointed to the upheaval created by a redesigned currency that has left many unable to obtain bank notes. The cash shortage affected transport not only for voters but also election workers and police officers providing security.

There were fears of violence on Election Day, from Islamic militants in the north to separatists in the south. Voting was largely peaceful Saturday, though a dramatic scene unfolded in the megacity of Lagos in the mid-afternoon.

Associated Press journalists saw armed men pull up to the voting station in a minibus, fire shots in the air and snatch the presidential ballot box. The shots sent voters screaming and scattering for cover, and ballots strewn across the floor.

And in the northeast state of Borno, at least five people including children, were wounded when Boko Haram extremists attacked voters in Gwoza town, local authorities said.

“The threat was neutralized by the troops of the Nigerian army who responded swiftly and chased the terrorists to the mountains,” said Abdu Umar, Borno's state police commissioner.

Mahmood Yakubu, head of Nigeria’s election commission, said voting would continue late into the evening in places that had recorded violence but now have an adequate security presence.

“We are determined that no Nigerian should and would be disenfranchised,” he said.

Analysts say it won't be clear how widespread and significant the delays and attacks on polling stations were until after the polls have closed.

“Despite the assurances of smooth and credible elections by the electoral commission, the voting process has been very complicated for Nigerians," said Mucahid Durmaz, senior analyst at Verisk Maplecroft, a global risk intelligence company. There have been “widespread complaints about late-arriving officials, nonfunctioning machines, low presence of security and attacks on polling stations," he added.

Incumbent President Muhammadu Buhari is stepping down after two four-year terms in Nigeria, a West African country where unemployment has soared to 33% even as one of the continent's top oil producers.

Out of the field of 18 presidential candidates, three front-runners have emerged in recent weeks: the candidate from Buhari's ruling party, the main opposition party candidate and a third-party challenger who has drawn strong support from younger voters.

But it remained unclear how many voters were deterred because of the cash crisis, which has left Nigerians with funds in their bank accounts unable to obtain the cash they need for things like gas and taxis.

Kingsley Emmanuel, 34, a civil engineer, said the cash scarcity was a real obstacle for many would-be voters.

“They don’t have the cash to pay for a commercial vehicle and most of them don’t accept (money) transfer,” he said from a polling station in the city of Yola in Adamawa state. “So it is very difficult for them to access their polling unit.”

“Thank God for my friend in the market that helped me with a little token. If not for him, I wouldn’t have been here,” said Onyekwere Goodness, who was at a polling station in Agulu.

The vote is being carefully watched as Nigeria is Africa's largest economy. By 2050, the U.N. estimates that Nigeria will tie with the United States as the third most populous nation in the world after India and China.

It is also home to one of the largest youth populations in the world with a median age of only 18. About 64 million of its 210 million people are between the ages of 18 and 35.

Favour Ben, 29, who owns a food business in the capital, Abuja, said she was backing third-party candidate Peter Obi.

“Obi knows what Nigerians need,” she said. “He knows what is actually disturbing us and I believe he knows how to tackle it.”

Buhari's tenure was marked by concerns about his ailing health and frequent trips abroad for medical treatment. Two of the top candidates are in their 70s and both have been in Nigerian politics since 1999.

By contrast, at 61, Obi of the Labour party is the youngest of the front-runners and had surged in the polls in the weeks leading up to Saturday's vote.

Still, Bola Tinubu has the strong support of the ruling All Progressives Congress party as an important backer of the incumbent president. And Atiku Abubakar has the name recognition of being one of Nigeria's richest businessmen, having also served as a vice president and presidential hopeful in 2019 for his Peoples Democratic Party.

Analysts have said it is one of Nigeria’s most unpredictable elections, with Obi as the surprise candidate in what is usually a two-horse race. But the ruling party’s Tinubu insisted Saturday he would prevail.

Asked if he would congratulate the winner of the election if it is not him, Tinubu retorted: “It has to be me!”

Abubakar also told reporters after voting Saturday that he was “very optimistic” about this year’s election.

For the first time this year Nigeria's election results will be transmitted electronically to headquarters in Abuja, a step officials say will reduce voter fraud. Officials also say they'll be enforcing a ban on mobile phones inside voting booths to prevent vote-buying: images of the votes are usually sent as proof if people have received money to pick a certain candidate.

Since officials in November announced the decision to redesign Nigeria's currency, the naira, new bills have been slow to circulate. At the same time, older bank notes stopped being accepted, creating a shortage in a country where many use cash for daily transactions.

Durmaz says the currency change should have been laid out in a longer timeline before or after the election. Lengthy waits to vote “will likely disenfranchise voters, deepen the electoral disputes and trigger violence.”

“Delays along with reports of voter suppression in Lagos risk aggravating the disappointment among passionate voters in a highly-anticipated election and cause an explosion of violent protests in urban centers,” he warned. “Any outbreak of violence could rapidly embrace ethnic and religious undertones, given the considerable impact of ethnic and religious differences on elections in Nigeria.”

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Associated Press journalists Grace Ekpu in Lagos, Nigeria; Yesica Fisch in Yola, Nigeria; Haruna Umar in Maiduguri, Nigeria; Dan Ikpoyi in Agulu, Nigeria; Krista Larson in Dakar, Senegal, and Sam Mednick in Ouagadougou, Burkina Faso contributed to this report.

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