Supporters ride in a campaign bus of leading opposition All Progressive Congress (APC) presidential candidate Mohammadu Buhari and his running mate Yemi Osinbajo as they drive past a campaign poster of Nigerian President and candidate to his re-elect ~ PIUS UTOMI EKPEI
Abuja - Problems with new technology on Saturday forced a 24-hour extension to the presidential election in Africa's most populous nation, Nigeria, and renewed Boko Haram violence hit the knife-edge vote.
The Islamist militants were suspected of killing seven in separate attacks in northeastern Gombe state, including at polling stations, while on Friday, 23 people were beheaded in Borno.
Also read: Voters brave Boko Haram bullets to cast ballots
President Goodluck Jonathan was the most high-profile victim of the glitches with handheld readers, which scan biometric identity cards to authenticate voters to help cut electoral fraud.
The 57-year-old, who is seeking a second term of office, was forced to abandon his attempt to accredit for the ballot in his home town of Otuoke, Bayelsa state, after the device repeatedly failed.
He was then accredited by hand and later voted but said afterwards: "As head of state, I don't blame anybody, I think the problem is national."
The Independent National Electoral Commission (INEC) accepted there had been "challenges" with the technology in "many" places that had forced polling officials to suspend the process.
INEC information commissioner Chris Yimoga said he could not give a figure on how many people were affected, with voters also reporting the late and even non-arrival of election officials.
"The problems are not in all the states of the country but in a few states and each of these (resident electoral commissioners) have been informed."
People in the affected areas will go back to the polls on Sunday, INEC said.
"This is very sad indeed," Peter Ogbuoni, a 31-year-old civil servant, said of Jonathan's problems as he waited to vote in Otuoke in the oil-producing southern Delta.
"If the president could spend more than 30 minutes without being accredited, I wonder how INEC will claim to have conducted a credible election?"
The Boko Haram threat has dominated the election campaign, with the Islamist militant group's leader Abubakar Shekau having threatened to disrupt the vote.
A spate of suicide bombings and attacks on "soft" targets such as markets and bus station raised fears about the safety of voters and led to stringent security measures to be put in place countrywide.
The rebels, who have recently been pushed out of captured territory in the restive northeast by a four-nation military coalition, appeared to hold good to that pledge by attacking Gombe state.
At least seven people were killed when suspected Boko Haram gunmen launched separate attacks in the neighbouring villages of Birin Bolawa and Birin Fulani, the town of Dukku and nearby Tilen village.
The first three attacks saw shots fired at voters at polling stations and election materials were burned.
An election official, who requested anonymity, said: "We could hear the gunmen shouting, 'Didn't we warn you about staying away from (the) election?'"
The beheadings happened in Buratai on the eve of voting, a nurse in Biu and lawmaker Mohammed Adamu, who represents the town some 200 kilometres (125 miles) from the Borno state capital, Maiduguri.
Voters turned out in force in Maiduguri, which has been repeatedly hit in the insurgency that has left more than 13,000 dead and some 1.5 million homeless.
Civilian vigilantes swept voters, many of them women widowed by the violence or separated from their husbands, with hand-held metal detectors.
"I am ready to cast my vote at whatever cost," said Tandalami Balami, who fled the recently liberated town of Gwoza to a camp in Maiduguri.
Jonathan, his main challenger Muhammadu Buhari and 12 other candidates are contesting the presidential poll, while 2,537 hopefuls from 28 parties are vying for 469 seats in parliament.
The president's ruling party has been in power since Nigeria returned to civilian rule in 1999 but the result is far from clear this time, with the opposition in its strongest position ever.
The president's inability to tackle Boko Haram until recently has dominated his tenure and while Nigeria became Africa's largest economy on his watch, global oil shocks have hit the country hard.
Even Jonathan has admitted that the election is close, with Buhari, a former military ruler, seen by some as an antidote to endemic government corruption and insecurity.
The technical glitches could not have come at a worse time for Nigeria, after it delayed the scheduled February 14 vote by six weeks on security grounds and after a previous postponement in 2011.
During the election campaign, Jonathan's Peoples Democratic Party repeatedly criticised the use of the technology, which is designed to "read" fingerprints and other personal data in 10 seconds.
It was backed by the main opposition All Progressives Congress (APC), whose candidate Buhari, was accredited without a hitch in his home town of Daura, in the northeast state of Katsina.
Voting had begun in many places at 1230 GMT, including in Maiduguri and Yola, the capital of neighbouring Adamawa, where polling units had been set up for people made homeless by Boko Haram violence.