Abuja - First results trickled in from Nigeria's closely fought general election on Monday, 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.US, UK warningThe PDP and the APC on Sunday 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.Wait and see 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.APC women's leader Victoria Nyeche said on Monday after police used teargas: "What happened today was unprecedented... All we want is a fresh election because what happened on Saturday was a fraud."Political parties have been urged to take any disputes to court rather than the streets.Call for calm Jonathan's PDP has been in power since Nigeria returned to civilian rule in 1999 but is being pushed to the wire by Buhari.The prospect of a democratic transfer of power - plus economic woes caused by the slump in global oil prices, concerns about corruption and fears about insecurity - energised the vote.The winning presidential candidate needs not just the most votes but at least 25% support in two-thirds of Nigeria's 36 states and the Federal Capital Territory to avoid a run-off.Voting was pushed into an unscheduled second day Sunday after failures in controversial new technology designed to read biometric identity cards to combat electoral fraud.Among those whose card did not work was the president himself.Some 348 polling stations had to open again on Sunday to complete the vote, for which 68.8 million people are registered out of Nigeria's population of 173 million.But election chief Attahiru Jega said the number of affected devices was minimal and the commission was confident of meeting its aim of a "free, fair, credible and peaceful" election."We appeal to all Nigerians to remain peaceful as they await the return of these results," he told a news conference on Sunday.Deadly attacks Boko Haram has dominated the campaign, with military operations against the Islamist militants forcing a six-week delay to the scheduled February 14 election.On Sunday, residents and a military source said soldiers supported by two fighter jets intercepted militants at Dungulbe village, seven kilometres (four miles) from Bauchi city in the northeast.A spokesperson for the Bauchi state governor said a round-the-clock curfew had been imposed on three areas because of the fighting.The militants were believed to have come through the town of Alkaleri, 60 kilometres away, where there was a dawn raid on Saturday.A series of suspected attacks on polling stations in neighbouring Gombe state on Saturday killed at least seven.Boko Haram leader Abubakar Shekau had vowed to disrupt the election, calling it "un-Islamic".