It was unclear how widespread the problems were, but the decision to extend the vote, which pits incumbent Goodluck Jonathan against his main rival, Muhammadu Buhari, added more uncertainty to an already tense election campaign.

　　Officials had already postponed the vote in February, citing security concerns from the Boko Haram insurgency, which has ravaged the country's northeast.

　　Technical Problems Mar Nigerian Election; Voting Extended By a Day

　　Voting Saturday was marred by an attack by suspected Boko Haram insurgents in the northeastern state of Gombe. Witnesses told VOA that gunmen attacked three villages in the state, killing at least 24 people.

　　Insurgents also killed 25 people in a Borno state village, in the northeast, on Friday, Governor Kashim Settima said.

　　Voting problems

　　Jonathan and the ruling Peoples Democratic Party are facing a tough challenge from Buhari and his opposition backers, the All Progressives Congress.

　　Past elections have been marred by allegations of vote rigging. Violence after the disputed 2011 elections, which also featured Buhari challenging Jonathan, killed some 800 people.

　　Election officials have touted a new biometric voter card system as insurance against fraud, but in some places, the hand-held readers appeared to malfunction.

　　Many polling stations opened late because of delays in getting voting materials and problems with the accreditation process. Polling places from Lagos, Nigeria's largest city, to Potiskum, in the country's far northeast, reported problems with the hand-held scanners.

　　As of Saturday night, the problems seemed to be more sporadic than systematic.

　　In the central city of Kaduna, people brought mats to polling stations to lie down and wait as voting continued into the night.

　　"As long as I can wait, even in the night, I'm willing to cast my vote. And I'm sure everybody on the queue is willing to cast his vote, no matter the time," said Abba Galadima, a civil servant.

　　Voters at one station in Lagos told VOA they waited in line for several hours while election workers looked for a machine that would work.

　　Jonathan, who cast his vote in the southern town of Otuoke, needed 30 minutes to go through the process.

　　At a station on the outskirts of the capital, Abuja, a VOA reporter watched officials struggle with the card-reader machines, trying to verify voter fingerprints. Some staff had voters use several different fingers, trying them multiple times but still not succeeding. Officials urged voters to wipe their fingers or wash their hands to try to fix the issue.

　　“Any government that is coming in, we want a change," said Yusuf Oriolow, 30. "We just need a change and we are changing Nigeria for better. That is what I see today.”

　　In Kano, a city of 2 million located around 300 miles north of Abuja, a VOA reporter visited multiple polling stations Saturday morning but found only one that had working card readers. About 100 people lined up at the station, waiting to cast their ballots, as well as a handful of security personnel and agents from the electoral commission.

　　Scuffles broke out in Rivers state in the southern Niger Delta over missing results sheets amid already high tensions and concerns about vote rigging. Election officials suspended voting in one area, and the state governor refused to vote.

　　A car bomb went off near a polling station in southeastern Enugu state, though no injuries were reported.?

　　The Independent National Electoral Commission announced that because of the technical problems, voting would be extended into Sunday.

　　"Whereas the process has gone on well in several places, in some others it has encountered some challenges, especially with the use of the card readers," the commission said in a statement on its website. "Consequently, accreditation has been slow in many places and has not commenced at all in some others."

　　Despite the delays, however, the vote appeared to be proceeding calmly.

　　"You can see the enthusiasm amongst the people. We want to exercise our vote," voter Samuel Eke told VOA in the southern city of Port Harcourt. "We have all the hope that materials were sent out to the various units. So maybe we'll give them some time."

　　The electoral commission's website went offline earlier Saturday when a hacker group calling itself the Nigerian Cyber Army attacked it, posting a message warning officials not to rig the polls.

　　Earlier in the week, both Jonathan and Buhari pledged to respect the outcome of the election as long as it was "free, fair and credible."

　　Jonathan, 57, is a Christian from the Niger Delta oil region in the south, while Buhari, 72, is a Muslim from the north. Pre-election polls showed the two in a very close race.

　　Preliminary results may be announced Sunday, though a final certified tally was not expected before Monday at the earliest.

　　Delayed in February

　　The vote was postponed in mid-February because of fighting and insecurity in the northeast where the Boko Haram insurgency has raged since 2009. The government's inability to stop the Islamist extremist group was a major issue during the campaign.

　　Security across Nigeria was tightened leading up to the election amid concerns that insurgents could attack polling stations.

　　In recent weeks, a multinational offensive drove Boko Haram from most of the towns it controlled in the northeast. On Friday, the Nigerian military said soldiers took back the town of Gwoza and destroyed the headquarters of Boko Haram's self-declared caliphate.

　　U.S. intelligence officials expressed caution about the report, saying that even if the militants had retreated, it did not necessarily mean they were 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 counterattack.

　　Stein and Ahmed reported from Kano. Also contributing was Katarina Hoije in Lagos, Ardo Hazzad in Bauchi, Ibrahima Yakubu in Kaduna, Kareem Haruna in Maiduguri and Hilary Uguru in Port Harcourt.