Nigerian President Muhammadu Buhari cast his ballot in the presidential election on Saturday as polls opened after a week-long delay, television images on Channels TV showed.
The race to control the country with Africa's biggest economy pits Buhari, who is seeking a second term, against main opposition candidate Atiku Abubakar, a businessman and former vice president. Analysts have predicted a tight race.
Buhari, who voted in his hometown of Daura in the northern state of Katsina, said "I will congratulate myself" when asked by reporters if he would congratulate his rival, should his rival win the election.
A Reuters witness said Atiku was expected to cast his ballot soon in Yola the capital of Adamawa state.
Nigerians queued at polling booths around the country, according to Reuters witnesses, with voting set to begin at 8:00 a.m. local time (0700 GMT). Some polling units across the country were, however, slow to open, Reuters witnesses said. The country has 72.8 million eligible voters.
In the country's northeast, where insurgent groups like Boko Haram and Islamic State West Africa Province have waged a decade-long war, blasts were heard in the city of Maiduguri, the capital of Borno state, said Reuters witnesses.
GRAPHIC-Nigeria presidential election: https://tmsnrt.rs/2E6qkDO
Meanwhile, residents in the village of Geidam in Yobe state, which neighbours Borno, said they fled an attack by suspected militants.
Boko Haram and its offshoot Islamic State West Africa Province have carried out deadly sporadic raids in Borno state. Boko Haram had warned people not to vote.
"We have along with our wives and children and hundreds of others fled. We are right now running and hiding in the bushes," said Geidam resident Ibrahim Gobi, speaking by phone.
Police said in a statement that there was no attack on any part of Maiduguri. Security sources told Reuters that militants had struck at parts of the city and a Reuters witness said he had heard gun shots and Nigerian air force jets were flying overhead.
The presidential vote in the continent's top oil producer and most populous nation is too close to call between Buhari and the main opposition candidate Atiku Abubakar, a businessman and former vice president who leads a field of more than 70 challengers.