Nigerians are finally going to the polls for the country's general election following a last-minute postponement of the vote a week ago.
The main challenger to President Muhammadu Buhari, 76, is the former vice president, Atiku Abubakar, 72.
Whoever wins will have to address power shortages, corruption, security threats, and a sluggish economy.
Voting began at 08:00 (07:00 GMT) and polls are due to close at 14:00 (13:00).
Reported attacks
About two hours before polls were due to open on Saturday, residents of the town of Maiduguri, the capital of Borno state in the country's north-east reported hearing several blasts and gunfire.
State police said in a statement that there was no threat to public safety. "The gunfire were not targeted at members of the public but was for security purposes," the statement said.
Borno is the birthplace of the Islamist militant group Boko Haram, which had said it planned to disrupt the elections.
In the north-eastern state of Yobe, suspected Islamist militants attacked the town of Geidam, forcing people to flee, the Reuters news agency reported.
Why was the election delayed?
The initial vote was rescheduled in a dramatic press conference in the early hours of Saturday 16 February, just five hours before polls were due to have opened.
The Independent National Electoral Commission (INEC) has given several reasons for the delay, including attempted sabotage and logistical issues such as bad weather and problems with delivering the ballot papers.
Inec has said that everything is in place for the poll to take place this time around.
How will the election work?
The candidate with the most votes is declared the winner in the first round, as long as that person gains at least 25% of the votes in two-thirds of Nigeria's 36 states.
There are 73 registered candidates in the presidential election, but campaigning has been dominated by the two political giants and the established party machines behind them.
The president's All Progressives Congress (APC) has promised to take the country to the "next level", arguing that in his first four-year term Mr. Buhari has done a lot of "foundational work" that may not be immediately obvious.
Mr. Abubakar and his People's Democratic Party have pledged "to get Nigeria working again", saying that the president has wasted the last four years.
Both men are from the mainly Muslim north of the country. While they are in their 70s, more than half of Nigeria's 84 million registered voters are under 35.
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