Rival refuses to accept result as president Muhammadu Buhari is declared winner after Nigeria election marred by deaths

Nigeria’s president Muhammadu Buhari Credit: Ben Curtis/AP

Nigeria’s top opposition candidate has rejected the result of what he called a "sham election" and said he will challenge it in court.

Nigeria’s president Muhammadu Buhari was earlier declared the clear winner of a second term in Africa’s largest democracy.

The former military dictator said he was "deeply humbled" by the result and expressed his regret after a violence-marred election that led to dozens of deaths.

But his billionaire challenger, Atiku Abubakar, has refused to accept what appeared an overwhelming result.

What was the scale of the declared victory?

15.1m

The votes for Mr Buhari.

11.2m

The votes for Mr Abubakar.

The electoral commission, which made its official declaration before dawn Wednesday, said the average national turnout was 35.6%, continuing a downward trend.

Mr Buhari's supporters began dancing in the streets of the capital, Abuja, on Tuesday night as vote counting stretched his lead from the weekend election to nearly four million votes.

Why hasn't the opposition accepted it?

Opposition’s presidential candidate Atiku Abubakar and his wife when casting their votes Credit: Sunday Alamba/AP

Prior to the result - in a failed last-ditch effort to stop the official declaration - Mr Abubakar’s party claimed that election data had been manipulated and demanded fresh elections in four of Nigeria’s 36 states.

Mr Buhari’s party rejected the accusations. It also called on Mr Abubakar, who has not made a public appearance since Saturday’s election, to accept his loss gracefully and concede.

The top opposition challenger, a former vice president, had made sweeping campaign promises to “make Nigeria work again”.

Why has this election been so troubled?

Supporters of President Muhammadu Buhari party celebrate in Abuja, Nigeria. Credit: Jerome Delay/AP

The election, once described as too close to call, suffered from a surprise week-long postponement and significant delays in the opening of polling stations.

While election observers called the process generally peaceful, at least 53 people were killed in an attack claimed by the Islamic State West Africa Province extremist group and other violence, analysis unit SBM Intelligence said.

A former US ambassador to Nigeria, John Campbell, said the troubled election had given the candidates grounds to go to the courts.

That route could now take months.