Official final results are yet to be announced but Buhari ended the race some 2.5 million votes ahead, marking the first democratic transfer of power in Nigeria’s history.

“I thank all Nigerians once again for the great opportunity I was given to lead this country and assure you that I will continue to do my best at the helm of national affairs until the end of my tenure,” he said in a statement.

“I have conveyed my personal best wishes to General Muhammadu Buhari.”

Jonathan’s public admission of defeat in the nail-biting election came more than six hours after he rang Buhari to concede, earning him widespread praise for statesmanship.

The rules state he must officially hand over on May 29.

Jonathan and Buhari last week signed a non-violence pact, seeking to avoid a repeat of previous elections which were marred by deadly post-poll clashes between rival supporters, exacerbated by ethnic and religious tensions. Jonathan urged disputes over the results to be settled in court rather than on the street.

Wild celebrations at 72-year-old Buhari’s victory broke out at the headquarters of his All Progressives Congress (APC) in Abuja and in cities across the Muslim-majority north.

The general, who first came to power three decades ago via a military coup, campaigned as a born-again democrat intent on cleaning up the corrupt politics of Africa’s most populous nation.

Buhari took power in a 1983 coup only to be thrown out 18 months later by another general. He subsequently embraced democracy, running in several elections and despite losing always bounced back.

He acknowledged the hard work ahead in building bridges. "I asked that we all be circumspect, respectful and peaceful ... We must begin to heal the wounds," he said.

But Jonathan said there should not be despair in his Peoples Democratic Party (PDP), which has governed Nigeria for all 16 years since military rule ended in 1999. “We have established a legacy of democratic freedom, transparency, economic growth and free and fair elections,” he added.

Jonathan, a Christian and the first head of state from the oil-producing Niger Delta, was thrust into the presidency in 2010 following the death of his predecessor Umaru Musa Yar’Adua, a Muslim from the north.

The mild-mannered Jonathan, often seen with his trademark fedora traditionally worn by Niger Delta natives, is from a family of boat makers. He became a zoology lecturer and worked on environmental issues before entering politics in 1998.

“I personally call him the accidental president. It was chance, good luck,” said Adewale Maja-Pearce, a Lagos-based writer and contributing columnist for . “He was plucked from obscurity because he was considered pliable.”

As for his distinctive name, his late father was quoted as saying in a biography of the president that he “called him Goodluck because although life was hard for me when he was born, I had this feeling that this boy would bring me good luck”.

His mother, Eunice, said although she had a history of lengthy labour in childbirth stretching for several days, Goodluck was born in record time.

Fortune certainly seems to have favoured Jonathan as he grew older.

An unconfirmed report has long circulated in local media that Jonathan, elected assistant senior prefect at his secondary school, grabbed the top post when the head prefect was expelled.

His rise to the top was similarly fortuitous, becoming governor of his native Bayelsa state in 2005 after his predecessor was impeached over money-laundering charges in Britain.

The night he was nominated by his People’s Democratic Party (PDP) as Yar’Adua’s running mate before 2007 polls, many Nigerians had never heard of Jonathan.

In one of the US diplomatic cables obtained by WikiLeaks, Jonathan purportedly acknowledged his inexperience in a meeting with the US ambassador while he served as acting president during Yar’Adua’s illness.

“I was not chosen to be vice-president because I had good political experience,” Jonathan said. “There were a lot more qualified people around to be vice-president.”

A magazine once described the Nigerian leader as “hardly a man to set the pulse racing”. Though always calm in public, Jonathan headed a nation plagued by a range of crises.

Nigeria is consistently ranked as one of the world’s most corrupt nations and the north is wracked by the brutal Boko Haram Islamist insurgency.

The main opposition All Progressives Congress had made Jonathan’s perceived failure to tackle both problems a central plank of its campaign.

Jonathan earned praise, however, for staffing his cabinet with internationally-regarded technocrats, notably ex-World Bank managing director Ngozi Okonjo-Iweala, who was his finance minister.

But despite living in Africa’s top oil producer, most of the country’s 173 million people live on less than US$2 a day and only receive a paltry supply of electricity.

Jonathan was accused of failing to take on such endemic problems.

“He has always said ‘Oh yes, we will take care of that,’” said Pat Utomi, a professor at Lagos Business School and prominent political commentator. “I think he meant to do well... but it seems there was never clarity in his head of where he wanted Nigeria to be.”

With additional reporting from Reuters