ABUJA (Reuters) - Nigerian President Goodluck Jonathan looked set for a close race against ex-military ruler Muhammadu Buhari on Saturday as results trickled in from a vote broadly deemed to have been the most credible for decades.
Tens of millions of Nigerians turned out for the polls, from the tin-roofed shacks of the Niger Delta, Jonathan's southern home region, to the dusty alleyways of Daura, Buhari's village in the mostly-Muslim north.
Early results showed Jonathan had done well in much of predominantly Christian southern Nigeria, including areas such as the most populous city of Lagos, where his ruling party had struggled in a parliamentary election a week ago.
But first results from heavily Muslim northern states showed Buhari with a wide lead and a high turnout which could outweigh his lack of support in the south. Tensions ran high in the north as Buhari's followers feared an attempt to rig the vote count.
"Across the country it will be close," former government minister Nasir el-Rufai, a Buhari supporter, told Reuters at a vote counting centre in the capital Abuja.
"My only fear is it will become a north-south issue if we see a situation where Buhari sweeps the north and Jonathan does well in the south. We may have to go to a run-off," he said.
To win in the first round, a candidate needs a simple majority and a quarter of the vote in two thirds of the 36 states. There are more than 73 million registered voters and 120,000 polling stations. Final results could take days.
A run-off between Jonathan and Buhari could risk polarising voters along regional lines in the country of 150 million, where ethnic and religious rivalries bubble near the surface.
Jonathan is the first head of state from the oil-producing Niger Delta. Should he become the first sitting president to lose an election, there could be protest in his home region.
But Buhari commands strong grass-roots support in the north, where some believe Jonathan is usurping their right to another four years in power. Jonathan inherited office after his predecessor, northerner Umaru Yar'Adua, died last year in his first term, interrupting a rotation between north and south.
"If Jonathan wins it's because he used his government power. It looks like he has done too well," said Habib Bazallahi, a local official from Buhari's party, leaning through a classroom window in the northern city of Kano to watch a vote count.
"Buhari says he won't go to court if he loses but that doesn't mean us, his supporters won't fight. We are ready. We're going to look for Kalashnikovs, bazookas ... There is no going quietly this time," he said, to cheers from the darkness.
There were tensions in other northern cities. Police were investigating a possible bomb blast in a brothel near a polling station in the city of Kaduna. The house of a local ruling party official was burned down in the town of Azere.
During voting, there was little sign of the chaos and violence that has dogged past elections although two bombs panicked voters in the troubled northeastern city of Maiduguri.
There were reports of underage voting and attempts at ballot-stuffing in some areas. In the northern state of Bauchi irate youths torched an electoral commission office after officials were allegedly found thumbprinting ballot papers.
"There are concerns that need to be addressed, but overall this is much better than the past," said Clement Nwankwo, head of the Policy and Legal Advocacy Centre (PLAC) in Abuja, working with more than 20 civil society groups to monitor the vote.
Election workers, party officials, observers and armed police crammed into classrooms around the country commandeered as collation centres. Heated arguments at one in Abuja flared and dissipated, but observers said the system was working.
"What we see appears to be logical and there is care being taken that what was counted out there is reflected in here," said former Canadian Prime Minister Joe Clark.
Nigeria has failed to hold a credible election since military rule ended just over a decade ago and observers said the voting process itself had been a vast improvement.
But that was always going to be the easy part. In the past the heaviest rigging has taken place in dimly-lit counting centres after voters have gone home.
"We are reaching the critical end when vote counting now starts ... that is when we need to remain continuously vigilant and peaceful," said Lagos state governor Babatunde Fashola.
(For full Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/ )
Additional reporting by Joe Brock and Mike Oboh in Kano, Shyamantha Asokan and Hannington Osodo in Lagos, Abdulwahab Muhammad in Bauchi, Samuel Tife in Otuoke, Ibrahim Mshelizza in Maiduguri; Editing by Matthew Tostevin