ABUJA, Nigeria — Election Day violence killed at least 39 people across Nigeria, civil society groups reported, and with ballot-counting halted and rumors flying, Nigerians were left waiting on Monday for an announcement of the winner in the presidential contest.
With President Muhammadu Buhari vying for a second term against more than 70 challengers, elections officials briefly halted the count, saying that results from Saturday’s voting had yet to be received from all districts.
The 18-hour gap until tabulation was to begin again Monday morning left time for more rumors to spread about whether the delay was helping the leading candidates rig the results. At one point, members of the party of the leading challenger, Atiku Abubakar, declared victory, a notion that was far from certain.
Much of the violence on Saturday played out in the south of the country, in opposition strongholds where the tight election is particularly contested, according to Cheta Nwanze, head of research at SBM Intelligence, a nonpartisan group that has been critical of the government and is tracking violence based on reports from local police and media.
Delays have been a reigning theme of Nigeria’s presidential election, which had been scheduled to take place a week earlier. To the frustration of many voters, the national electoral commission, citing logistical issues, postponed the vote in the middle of the night, just hours before polling places were to open.
Both Mr. Buhari, 76, and Mr. Abubakar, 72, a businessman and former vice president, spun theories about the delay, each claiming that the commission was stalling to gain an advantage for the other camp.
When the vote finally took place on Saturday, most polling stations did not open until four hours after the official starting time, civil society groups reported. Some opened so late that they had to reopen on Sunday to give voters the six hours allotted to cast ballots — one reason cited by election officials for delaying the tabulation.
It became apparent on Sunday and Monday that violence on Election Day had been worse than originally reported.
One election worker was killed by a stray bullet in Rivers State, a restive region where six civilians and one soldier also died in a shootout, in a separate incident, according to civil society groups. In the same state, some election workers and police officers were taken hostage, but released unharmed, the groups said.
In Lagos, one of Africa’s most populous cities, violence broke out at polling places, with shots fired in the air and ballot boxes set on fire, the groups said, adding that some voters rioted when election materials did not arrive on time.
“No election in Nigeria should cost the life of any citizen,” said Clement Nwankwo, executive director of the Nigeria Civil Society Situation Room, a coalition of groups monitoring election issues.
At a news conference Monday morning, Mr. Nwankwo was critical of Mr. Buhari’s statements that anyone caught trying to rig the vote would be killed, suggesting the message incited violence.
Mr. Nwankwo also criticized the deployment of the military to provide security for elections, calling the act “totally, totally unacceptable.” He noted that soldiers had been involved in the shootout in Rivers State and had blocked voters from reaching the polls in some areas.
“They are not needed,” Mr. Nwankwo said, recalling the 1980s, when Mr. Buhari, then a general, was in power under a military regime. “We have suffered years of military rule in this country.”
He urged Britain and the United States to impose sanctions on any political figures whose actions led to deaths.
In a room down the hall from where Mr. Nwankwo presented his findings to the public, the African Union minutes later offered a glossier view of the elections, citing a small number of irregularities.
“Over all, generally the process was peaceful and orderly,” said Hailemariam Desalegn, former prime minister of Ethiopia, who was in charge of the bloc’s observer mission in Nigeria.
Other election observers noted that as bad as the violence was this year, prior elections have been worse. One local observer mission reported that the irregularities and issues with the election had occurred in what was a small percentage of the thousands of polling stations, which were set up to handle more than 70 million voters in Africa’s most populous nation.
Mr. Buhari was elected in 2015 after three earlier, unsuccessful runs for the presidency. In office, he has spent months abroad receiving medical treatment for unspecified health problems, and has been unable to stamp out the Islamist Boko Haram insurgency.