Millions of Nigerians headed to the polls Saturday to cast ballots in the tightest presidential election since the West African nations returned to civilian rule in 1999.
Most eyes are on President Goodluck Jonathan and his ruling Peoples Democratic Party, which face a tough challenge from former military ruler Muhammadu Buhari and the opposition All Progressives Congress.
The Independent National Electoral Commission is hoping to prevent fraud with a new biometric voter identification system. Past elections have been marred by allegations of fraud, including in 2011 when some 800 people were killed in sectarian violence and rioting.
Some Nigerian media reported on Saturday reported that the hand-held electonic readers used to read Permanent Voter Cards were having trouble reading voters' fingerprints.
In some polling places, election staff were reported to have arrived late, the delivery of voting materials was delayed, and other technical problems.
Earlier in the week, both Jonathan and Buhari pledged to respect the outcome of the election as long as it is "free, fair and credible."
Jonathan, 57, is a Christian from the Niger Delta oil region in the south, while 72-year-old Buhari is a Muslim from the north.
The vote was delayed from mid-February because of fighting and insecurity in the northeast where the Boko Haram insurgency has raged since 2009. Jonathan's inability to stop the militant group has plagued his campaign.
Security across the country has been tightened leading up to the election amid concerns the insurgents could attack polling stations.
On Friday, the military claimed soldiers took back the town of Gwoza, one of the last areas in the northeast controlled by Boko Haram. The military said it destroyed the headquarters of Boko Haram's self-declared caliphate.
U.S. intelligence officials expressed caution about the report, however, saying that even if the militants had retreated, it does not necessarily mean they are near defeat.
Intelligence officials told VOA that Boko Haram has used strategic retreats in the past only to wait, sometimes for weeks or more, for an opportunity to launch a devastating counter attack.
Jonathan urges peaceful vote
In a nationally televised address Friday, Jonathan commended the armed forces and called on all Nigerians to refrain from violence.
"The nation's security agencies are also fully prepared and ready to deal decisively with any group or persons who attempt to disrupt the peaceful conduct of the elections or cause any form of public disorder," he said.