Thousands of people spilled into the streets of northern Nigeria's biggest city, Kano, yesterday to celebrate as opposition presidential candidate Muhammadu Buhari claimed victory in the election. A cavalcade of motorbikes and cars with their headlights on and horns blaring paraded through the streets of the ancient seat of learning, now a commercial hub.The opposition All Progressives Congress declared victory for its candidate, former military ruler Buhari, yesterday and said Nigeria was "witnessing history".Its spokes man, Lai Mohammed, said: "The people of Nigeria have taken over."He said the APC had no reason to doubt that President Goodluck Jonathan would concede defeat."He said several times that he would relinquish power if he were voted out in a free and fair election," Mohammed said.Buhari ruled between 1983 and 1985 after seizing power in a coup. Ousted himself in another military takeover, led by General Ibrahim Babangida in August 1985, he declared himself a convert to democracy and has since run, and lost, in several elections.Jonathan's five years at the helm of Africa's most populous country and biggest economy have been plagued by corruption scandals and a Boko Haram Islamist insurgency. His People's Democratic Party has run Nigeria since the end of military rule in 1999.Bar some technical glitches and the killing of more than a dozen voters by Boko Haram terrorists in the northeast, the election has been the most orderly in recent history.Violence and chaos were significantly less than in previous elections in this country of 170million.The relatively orderly conduct also eased fears of a repeat of the violence that followed a Buhari defeat to Jonathan in 2011, when 800 people were killed in three days of blood-letting in the predominantly Muslim north."There are probably lots of reasons why the PDP might have lost, but I think the key one is that the elections just haven't been rigged," said Antony Goldman, a business consultant with high-level contacts in Nigeria.In the Abuja house in which Buhari is living there was restrained joy - befitting his image as a sandal-wearing Muslim ascetic - tinged with a sense of the responsibility victory will bring. Buhari will have to manage the power transition in a country with a long history of political violence."We should all work together to redirect the country," senior APC official Bukola Saraki said. "A lot of sacrifices will have to be made."Buhari's march to victory was briefly interrupted when Godsday Orubebe, a former minister from the Niger Delta province, grabbed a microphone and launched into a 10-minute rant against election commissioner Attahiru Jega at the commission's headquarters in the capital.Orubebe was eventually persuaded to end his protest and put down the microphone, allowing the results announcements ceremony to continue.As Buhari's vote tally mounted, flashpoint northern cities such as Kaduna and Kano were quiet, helping push the stock market up almost 1% to a three-week high."With projections that Buhari might eventually be announced as president-elect, it sends a positive signal to markets that there could be a change to the way things have been done in the past," Ayodeji Ebo, head of research at Afrinvest said.Although Nigeria's economy has been growing at 7% or more, scandals over billions of dollars in missing oil receipts, and the rise of the Boko Haram insurgency, in which thousands have died, have undermined Jonathan's popularity.The president's slow reaction to the kidnapping of more than 200 schoolgirls from the village of Chibok in April last year by Boko Haram caused widespread anger.Buhari campaigned on his reputation as a military strongman who could crush Boko Haram and gain the confidence of northern Muslim leaders.The war has turned in Jonathan's favour in the past six weeks - but too late to gain him much credit in the election...