Nigeria's President Muhammadu Buhari on Wednesday formally submitted his candidacy to stand for a second term of office at elections in February next year.
The 75-year-old leader traveled to the headquarters of his ruling All Progressives Congress (APC) party in the capital Abuja to hand in his nomination form.
He was accompanied by state governors, government ministers and party supporters.
He said afterwards he was seeking the nomination "with all humility, sense of responsibility and an unquestionable desire to serve and protect the interest of all Nigerians."
Well-wishers and supporters clubbed together to pay the 45 million naira ($125,000, 108,000 euros) for the nomination form.
"I assure them and the rest of Nigerians that if nominated and if elected, I shall continue to serve you to the best of my ability," Buhari said.
Former military ruler Buhari in 2015 became the first opposition candidate in Nigerian history to defeat a sitting president at the polls.
He was elected in the landmark election on a platform to improve security, tackle endemic corruption and boost the economy.
But despite Boko Haram Islamists remaining a threat to security, his anti-corruption campaign is making slow progress while the nation recovers from recession.
There have been questions, too, about Buhari's fitness to govern after he spent months being treated for an undisclosed illness in London last year.
Buhari told his supporters to guard against complacency "but to prepare, strategize and win 2019 elections".
The APC has been hit by a wave of defections to the main opposition People's Democratic Party (PDP), with critics unhappy at his perceived autocratic style.
In a dig at the PDP, Buhari added: "We must not allow those who brought the country to its knees from 1999 to 2015 to come and take us back."
The APC has scheduled presidential primaries for later this month but a party spokesman told AFP no one else has picked up a nomination form, making Buhari the only candidate.
The PDP has extended its closing date for submissions of interest to stand in presidential primaries and will choose its candidate by October 6.
Among those who have already declared their intention to stand are former vice-president Atiku Abubakar and the leader of the Senate, Bukola Saraki.