Election officials declared ruling party candidate Bola Tinubu the winner of Nigeria’s presidential election early on Wednesday, with the two leading opposition candidates already demanding a revote in Africa’s most populous nation.

The overnight announcement was likely to lead to a court challenge by his main opponents Atiku Abubakar and Peter Obi. Mr Abubakar also finished second in the last vote in 2019, then appealed against those results before his lawsuit ultimately was dismissed.

On Tuesday, the two leading opposition parties had demanded a revote, saying that delays in uploading election results had made room for irregularities. The ruling All Progressives Congress party urged the opposition to accept defeat and not cause trouble.

Mr Tinubu received 8,794,726 votes, while Mr Abubakar came in second with 6,984,520. Mr Obi, the third place finisher, got 6,101,533 votes, according to the results announced live on television by the Independent National Electoral Commission.

The announcement came after 4am, but celebrations had already started late on Tuesday at the ruling party’s national secretariat where Mr Tinubu’s supporters had gathered in anticipation of his victory.

“None of the others matches his record,” said Babafemi Akin as he chatted excitedly about the prospects of a Tinubu administration. “I am sure he will do well”.

The parties now have three weeks to appeal against results, but an election can be invalidated only if it is proven the national electoral body largely did not follow the law and acted in ways that could have changed the result.

The Supreme Court of Nigeria has never overturned a presidential election, though court challenges are common, including by outgoing President Muhammadu Buhari, who doggedly fought his past election losses for months in vain.

Observers have said Saturday’s election was mostly peaceful, though delays caused some voters to wait until the following day to cast their ballots.

Many Nigerians had difficulties getting to their polling stations because of a currency redesign that resulted in a shortage of bank notes.

The president-elect thanked his supporters in the capital, Abuja, after his victory was announced and struck a reconciliatory tone in a message directed at his political adversaries.

“I take this opportunity to appeal to my fellow contestants to let us team up together,” Mr Tinubu said. “It is the only nation we have. It is one country and we must build together.”

Mr Tinubu, 70, is the former governor of Lagos state, home to Nigeria’s megacity of the same name. However, he lost the state in Saturday’s election to Obi, who drew a strong following among younger voters eager for change.

The tightly contested election has redrawn Nigeria’s electoral geography and produced results that are significantly different from those of past polls, with this being the first time that a president takes office with less than 50% of the vote and where four candidates won over a million votes, say analysts.

Mr Tinubu “will have to strive to win the support of the larger majority who preferred one of the other candidates, particularly the youth, the Christian groups that were opposed to his Muslim-Muslim ticket and Igbos in the south east who again feel denied the presidency,” said Nnamdi Obasi, senior adviser on Nigeria for the International Crisis Group.

From the onset, Mr Tinubu will have to contend with challenges to his legitimacy, so he will need to ensure an inclusive government and focus firmly on rebuilding national cohesion, he added.

Mr Tinubu clinched victory in part because the opposition vote was split and because his party had the strongest push to get people out to vote, said Amaka Anku, Africa director at the Eurasia Group consultancy.

Nigeria’s current president, Muhammadu Buhari, congratulated his successor in a statement on Wednesday, but said the election was not perfect.

“Of course, there will be areas that need work to bring further transparency and credibility to the voting procedure. However, none of the issues registered represents a challenge to the freeness and fairness of the elections,” he said.

The West African regional bloc, known as ECOWAS, called on political parties to appeal to their supporters to exercise maximum restraint and refrain from using provocative language, which would only “exacerbate political tensions, divisiveness, and violence at this critical stage”, said the group in a statement.