By Felix Onuah and Camillus Eboh

ABUJA - Nigeria's new president-elect, Bola Tinubu, called on citizens to unite around him on Wednesday, as he defended the integrity of the national election he won amid a bitter dispute over the results.

Both of the two main opposition parties have rejected the outcome as fraudulent, and said they would challenge the results in court. The bitter dispute has raised fears of violence in Africa's most populous nation and leading energy producer, which has a long history of electoral violence.

In past polls, street gangs with loyalty to Tinubu in the commercial hub of Lagos have fought pitched battles with gangs loyal to rival parties.

"I am very happy I have been elected the president of the federal republic of Nigeria," Tinubu said to cheers in Abuja. "This is a serious mandate. I hereby accept it."

He now faces a litany of national problems, including Islamist insurgencies in the northeast, armed attacks, killings and kidnappings, conflict between livestock herders and farmers, cash, fuel and power shortages, and deeply entrenched corruption.

The Independent National Electoral Commission (INEC) said Tinubu garnered 37%, or 8.79 million votes, in the weekend election, ahead of main opposition challenger Atiku Abubakar's 29%, or 6.98 million votes.

Peter Obi, an outsider popular with younger and more educated urban voters, won 25%, or 6.1 million votes.

A candidate can win by getting more votes than any of their rivals, provided they get 25% of the vote in at least two-thirds of the 37 federal territories - that is the 36 states and the federal capital territory of Abuja, which Tinubu managed to do.

LOW TURNOUT, LOW TRUST

With total votes cast at just under 25 million, out of 87 million people with voter identity cards and eligible to vote, turnout was only 29% - low, even by Nigerian standards. The 2019 election saw 35% turnout.

At least some of them were unable to vote due to malfunctioning of voter card reading machines.

Nigeria's election was meant to be its fairest and most open contest to date. But the electoral process encountered problems, owing to new technology that did not function well and seemed to overwhelm Nigeria's notoriously inadequate communications network. That undermined trust in the whole process.

"In the eyes of God, the man (Tinubu) is not the winner," trader Mercy Efong said in Akwa, in Obi's home state of Anambra.

The INEC had promised to upload results from each polling unit to its website in real time, but most units were unable to do so immediately. That was not a legal requirement, but it meant results had to be collated manually inside ward and local government counting centres as in previous polls, reneging on a policy that was meant to improve transparency.

"President Buhari said that he would do free and fair election (but) INEC is now turning everything upside down," said rickshaw driver Nedu Chukwunata, referring to the outgoing president.

"We want justice in Nigeria; we want democracy here in Nigeria ... we want our voice to be heard we are tired of corruption," said Chukwunata, who had parked his yellow rickshaw on a sandy patch of ground in Akwa.

'CREDIBLE ELECTION'

Observer missions have criticised the problems as the result of poor planning.

"I commend INEC for running a credible election no matter what anybody says," Tinubu said. "The lapses that were reported, they were relatively few in number and were immaterial to affect the final outcome of the election."

President Muhammadu Buhari, also from the All Progressives Congress (APC), congratulated his successor.

"Elected by the people, he is the best person for the job. I shall now work with him and his team to ensure an orderly handover of power," he said in a statement.

As Lagos governor, Tinubu won praise for partially fixing some of the cities problems, including reducing violent crime, waste collection and traffic.

The 70-year-old has, however, sometimes appeared frail in public, slurring his speech, answering questions with platitudes and skipping several campaign events, leaving some to doubt how effective or dynamic he will be as leader.