Nigeria's President Muhammadu Buhari has put the fight against corruption at the heart of his bid for another four-year term, as official campaigning got underway for elections next year.

At a campaign launch in the capital Abuja, he maintained he had delivered on his promises to improve security, the economy and tackle corruption.

But he accepted there was still work to do so everyone can benefit, not just the few, adding: “Our choices will shape us, our economic security and our future prosperity.

“Nigeria, more than ever before, needs a stable and people-focused government to move the agenda for our country forward.”

Soon after coming into office, Buhari pledged to recover what he said were “mind-boggling” sums of public money stolen during previous administrations.

His anti-corruption campaign, however, has yet to secure any high-profile convictions while his opponents accuse him of mounting a political witch-hunt.

On Sunday, he said graft remained “an existential threat” and that despite some gains, “there is still much ground to cover to stop systemic corruption”.

“We are committed to deepening the work we started this first term such that the nation's assets and resources continue to be organised and utilised to do good for the common man.”

Buhari said Nigeria had a chance to make “a break from its tainted past which favoured an opportunistic few”.

Despite the president's focus on tackling corruption, there have not been any significant convictions related to graft in his first term. The main opposition party has accused Buhari of focusing on its members, which the presidency denies.

The campaign team of opposition candidate, former vice president Atiku Abubakar, said Buhari's manifesto was an “anti-climax” and did not address Nigerians' economic problems.

“If the state of the average Nigerian has not improved in the last three and a half years, more of the same is obviously not what they need,” it said in an emailed statement.

The president set education as a policy priority, vowing to overhaul buildings and subjects taught at 10,000 schools in each year of the four-year term, and retrain teachers to focus on science, technology and mathematics.

He said there was “scope for over 15 million new jobs” by expanding a nationwide vocational skills programme and improving access to credit for entrepreneurs and artisans.

Buhari's response to an escalation of violence in the long-running resource conflict between farmers and herders in central states has been perceived as lukewarm.

His political opponents — even within the APC — have accused him of using the security and anti-corruption agencies to target them, leading to a wave of defections.

Nigerian elections since the country returned to civilian rule in 1999 after decades of military control have been characterized by deadly political violence.

Twenty-four countries and the European Union meanwhile called for “free, fair, transparent and peaceful elections” as campaigning began.

“We urge all involved — political and non-political actors — to refrain from using hate speech and take a firm stance against violence,” they said in a joint letter.

The signatories, including the United States, Britain, France and Germany, said they were “gravely concerned” about vote-buying, intimidation and interference in recent state governorship elections and party primaries.

(CGTN)