Nigerian President Muhammadu Buhari won a second term to lead the most populous country in Africa, the country's elections authority said Wednesday, while his main opponent promised to challenge the result in court.
Buhari defeated Atiku Abubakar, a former vice president and businessman, by about 4 million votes.
Turnout was nearly 35 percent of Nigeria's 82 million registered voters, the electoral commission said.
"I thank the millions of Nigerians who voted to re-elect me as your president for the next four years," Buhari said in a statement. "I am deeply humbled and profoundly grateful to you for judging me worthy of continuing to serve you and for your peaceful conduct."
Just hours before it was set to begin on Feb. 16, the electoral authority delayed the vote by a week, citing logistical challenges. Turnout likely fell after many Nigerians took lengthy bus rides across the country to vote in their hometowns, but could not afford to return the following weekend.
On Wednesday, Abubakar called the election result a "sham" and said he would challenge it in court. He accused soldiers in some Nigerian states of turning "their guns on the very citizens they were meant to protect." He also said it was a "statistical impossibility" that there was higher voter turnout in areas "ravaged by the war" against terrorist groups, like Boko Haram, and there were voting disruptions in his party's strongholds.
Abubakar's party, the People's Democratic Party (PDP), called for fresh elections in four states.
"I think it's very unlikely that the election may be repeated, but it depends on the courts," political analyst and editor-in-chief Mannir Dan-Ali of Nigeria's Daily Trust newspaper told NPR's Ofeibea Quist-Arcton. "But it's sometimes long drawn, it can take quite a while before the whole challenge is seen through."
At least 53 people have died in election-related violence, according to a report by SBM Intelligence and cited by The Associated Press. Buhari said the "elections were relatively peaceful," but that "troublemakers in a handful of states attempted to disrupt an otherwise orderly process" and he was "very sad at the grievous loss of lives."
In his victory statement, Buhari said his priorities for his next term would be to intensify efforts to bolster Nigeria's security, restructure the economy from its dependence on oil and fight corruption.
With a population of more than 200 million, Nigeria is Africa's most populous country and largest economy, but it remains heavily dependent on oil revenues. "The country is still emerging from a recession and needs to jump-start the economy," Quist-Arcton reports from Abuja.
Buhari, 76, was first elected in 2015 on an anti-corruption platform. He previously ruled the country as a military strongman in the 1980s before re-emerging in politics, saying he embraced democratic values.
Despite Buhari's attention to corruption, Nigeria continued to rank high in perceptions of corruption in the last few years, according tracking group Transparency International's 2018 index. The group said Buhari "took a number of positive steps in the past three years," but "these efforts have clearly not yielded the desired results. At least, not yet."
The other pressing issue for Buhari to address is the ongoing violence in the country's northeast connected to the Boko Haram insurgency and conflicts between herders and farmers in central Nigeria. Twenty-nine bodies have been recovered after the latest fighting between herders and farmers on Tuesday, according to The Associated Press, while a group claiming affiliation with Islamic State said it attacked a town on election day.
NPR's Ofeibea Quist-Arcton contributed to this report.