Bola Tinubu from Nigeria’s ruling party has taken a strong lead as results are declared from Saturday’s presidential election, amid opposition protests.
With results announced from about two-thirds of the states, he has a lead of about 1.5 million votes.
Mr Tinubu, 70, a wealthy businessman and former governor of Lagos state, has 39% of votes counted so far.
Former Vice-President Atiku Abubakar has 31%, while third-party candidate Peter Obi has 20%.
The parties of both Mr Abubakar and Mr Obi have called for the election to be cancelled and rerun, alleging that the inability of the electoral commission to upload results to its website showed that the results had been manipulated.
Many voters reported widespread problems with uploading results through the new electronic voting system, which was intended to speed up the process.
There were also widespread delays, with many polling stations opening several hours late, and some attacked by armed men. Voting was held overnight, and on Sunday in some areas.
The electoral commission says the opposition parties should take their complaints to court and is pressing ahead with the release of results.
A candidate needs to have the most votes nationwide and at least a quarter of ballots cast in 25 of the 36 states, plus Abuja, to be declared the winner.
If those thresholds are not reached then there will a second round run-off between the top two candidates.
So far, Mr Tinubu has passed that threshold in 22 states.
Earlier on Tuesday, a group of angry protesters denounced the electoral commission, known as Inec, outside the national collation centre in the capital, Abuja.
“Everything happening there is all lies, all lies, lies… they are cooking up results,” one man told the BBC.
Another group held a counter-protest, urging the electoral commission to “complete your job” and calling on “Nigerians to stand up for democracy”.
European Union observers said the electoral body’s poor planning and communication had undermined trust in the process.
The ruling All Progressives Congress (APC) and Mr Atiku’s Peoples Democratic Party (PDP) have dominated Nigeria since the end of military rule in 1999.
Mr Obi ran for president for the first time, promising to challenge the two-party system.
He has the support of many young people, who make up a third of registered voters. There are 15 other candidates.
