Nigerian opposition candidate Muhammadu Buhari has won the country's presidential election as the incumbent Goodluck Jonathan apparently conceded defeat.

Mr Buhari, who was a former military ruler of the nation in the 1980s, is thought to have received 15.4 million votes compared to Mr Jonathan's 13.3 million.

Mr Jonathan, who has Nigeria for the last five years, congratulated the All Progressives Congress candidate by telephone on winning the weekend election, said an APC spokesman.

Lai Mohammed said: "I think he conceded defeat. There had always been this fear that he might not want to concede but he will remain a hero for this move.

"The tension will go down dramatically. Anyone who tries to foment trouble on the account that they have lost the election will be doing so purely on his own."

It was the fourth attempt by the former general at claiming the presidential prize and he has accused the ruling PDP Party of rigging the vote in all three previous contests.

Speaking to Sky News, the 72-year-old challenger admitted to being a little tired after an election campaign which saw him visit 35 of the country's 36 states as well as travelling to London to talk to British opinion-makers.

He spoke passionately about his desire to restore morale amongst his countrymen and women, crackdown on Nigeria's rampant corruption and rout Boko Haram militants.

He has repeatedly tried to lay to rest the ghosts of his past on the campaign trail after obtaining a reputation as a hardline military ruler when he first took up the presidential reins in 1983 after the army ousted the elected leader in a coup.

He himself was deposed in another coup two years later and jailed.

Since then Mr Buhari says he has undergone a dramatic conversion from military dictator to democracy-lover.

It was the fall of the Soviet empire - achieved without the "firing of one bullet" - which he attributes to his dramatic political change of heart.

Now though, with Nigeria's soldiers largely demoralised and complaining of poor pay, few weapons and little leadership, and a violent extremist insurgency in the north, suddenly his military background is becoming a positive asset.

Mr Buhari said: "With my background as a military man, we have to restore morale, with retraining and reorganisation.
"I am confident the military will respond favourably to me.

"Nigeria has the capacity to deal with Boko Haram.

"Nigerians are being killed in their hundreds every day and our (current) leadership sleeps soundly.

"I assure you that wouldn't happen under my leadership."

Image: Opposition candidate Gen. Muhammadu Buhari holds his ballot paper in the air before casting his vote in his home town of Daura, northern Nigeria Saturday, March 28, 2015 (AP Photo/Ben Curtis)