Abuja: First results trickled in from Nigeria's closely fought general election on Sunday, with protests over the conduct of the vote and a warning of manipulation of the count adding to fears of violence.
The presidential election pitting President Goodluck Jonathan against former military ruler Muhammadu Buhari is the closest in Nigeria's history, and the first with a credible opposition challenge.
International election observers gave broadly positive reactions to the conduct of the vote, despite late delivery of election materials and technical glitches with new voter authentication devices.
Nigeria's Transition Monitoring Group, which had observers across the country, said: "These issues did not systematically disadvantage any candidate or party."
The first nine results were announced in Abuja. Buhari and his All Progressives Congress (APC) won five states while Jonathan of the Peoples Democratic Party (PDP) took three plus the Federal Capital Territory, which includes Abuja.
But the PDP was marginally ahead on the overall number of votes won so far. More results will be announced from 1900 GMT.
The PDP and the APC today traded allegations of rigging and other irregularities, which raises the possibility of a legal challenge to the results.
Violence has often flared in previous Nigerian votes after the winner is announced and the United States and Britain warned of any rigging in the count.
"So far, we have seen no evidence of systemic manipulation of the process," Secretary of State John Kerry and foreign minister Philip Hammond said in a joint statement.
"But there are disturbing indications that the collation process -- where the votes are finally counted -- may be subject to deliberate political interference," they added.
Kayode Idowu, spokesman for the Independent National Electoral Commission (INEC) told AFP that there was "no basis" for the claim.
"There is no interference at all... We have no evidence of political interference," he said.
Kaduna state, one of the areas worst-affected by violence four years ago when some 1,000 people were killed in post-election clashes, was said to be calm.
But there were mixed sentiments in the largest city in the north, Kano.
"Election violence doesn't pay anybody. I think Nigerians have learnt from the fallout of 2011 and they are ready to be peaceful... And behave responsibly," said civil servant Salawu Abubakar.
But Suleyman Maaji, who also works for the government, added: "A lot of people decided to stay behind closed doors because they don't know, they are afraid. They don't know what might happen."
Some 2,000 women protesting against the conduct of the elections were teargassed as they tried to converge on the local electoral commission offices in the southern oil city of Port Harcourt.