Nigerian President Muhammadu Buhari has been re-elected for a second four-year term, the election commission says.
The 76-year-old defeated his main rival, former Vice President Atiku Abubakar, with a margin of nearly four million votes.
Mr Abubakar’s People’s Democratic Party (PDP) has rejected the result. Turnout was 35.6%.
Delays and violence marred the run-up to Saturday’s poll but no independent observer has cited electoral fraud.
Mr Buhari’s All Progressives Congress (APC) won in 19 of the 36 states while the PDP was victorious in 17 states and in the capital, Abuja, according to the electoral commission (Inec).
“The new administration will intensify its efforts in security, restructuring the economy and fighting corruption,” Mr Buhari said after his victory was officially announced.
The APC had 15.2 million votes while the PDP had 11.3 million.
Some supporters of Mr Buhari took to the streets late on Tuesday in celebration.
Who is Buhari?
A former soldier, Mr Buhari led a military regime for 20 months in the 1980s and was first elected president in 2015, becoming the first opposition candidate to defeat an incumbent and win the presidency.
His record in office is mixed. Mr Buhari’s critics say that the very attributes that won over voters four years ago – his strictness and inflexibility – have emerged as liabilities. They accuse him of autocratic leanings as well as a disastrous tendency towards inaction.
Mr Buhari’s supporters can argue that he has largely delivered on campaign pledges such as tackling corruption and cracking down on Boko Haram. But they may struggle to point to concrete achievements in other fields, such as fixing the economy.
The breadth and depth of corruption is so great, it affects so many aspects of public life that making serious inroads into the problem would require a focus, energy and application that was lacking in President Buhari’s first term.
The second problem he faces in fighting corruption is having the necessary political support. There is undoubted public backing but Mr Buhari’s party is compromised by senior members suspected of enriching themselves through graft. The fear is that across the board the looters will carry on pretty much as normal.
Economically, ending the dependency on oil revenues needs to happen at a much faster pace. The World Bank has predicted sluggish economic growth: 2.2% for the coming year in a country with unemployment of more than 20% and nearly half the population living in extreme poverty
President Buhari also faces an array of security threats from clashes between farmers and herdsmen in the Middle Belt, continuing instability in the Niger Delta and – most worrying of all – a revived threat from Islamic extremists in the north of the country.