Nigeria's newly elected leader Muhammadu Buhari said Wednesday he would "spare no effort" to defeat the Islamist militant group Boko Haram. "Boko Haram will soon know the strength of our collective will. We should spare no effort," Buhari said in his first formal speech since winning the presidential election. "In tackling the insurgency, we have a tough and urgent job to do."

The president-elect's pledge came as the head of the Catholic Church in Nigeria urged him to tackle corruption and wipe out Boko Haram. Cardinal John Onaiyekan said Nigeria must deal with Boko Haram’s insurgency to gain stability. “We have a very bad record on corruption,” Onaiyekan told Radio Vaticana Tuesday. “And there is no doubt this is pulling our nation down.”

Buhari, who was a military dictator in the 1980s, won Nigeria’s presidential election Tuesday over incumbent Goodluck Jonathan, who conceded defeat. The candidate from the All Progressives Congress won largely on a campaign focusing on security and corruption. One of Buhari’s most crushing victories came in the northern, Muslim state of Kano, where he won 1.9 million votes compared with Jonathan’s 215,799. Nigeria’s second most populous state is one of the areas hit hardest by Boko Haram, according to the Associated Press.

Buhari, 72, pledged during his campaign to fight Boko Haram while reforming the national army. He played up his military background while distancing himself from his authoritarian past. 

Jonathan’s administration and the long-ruling People’s Democratic Party suffered from rampant corruption. More than 70 percent of the federal budget was spent on the salaries and benefits of public officials under Jonathan’s administration.

Nigeria’s 2011 elections were plagued with violence after the results were announced, and there was initial fear that 2015’s elections might have a similar outcome. Onaiyekan credited the candidates’ pre-election agreement to accept the results with keeping the peace. He said there is “always a danger” for a violent reaction, but called the risk less severe than in the past.

Onaiyekan also called for increased “national cohesion” among Nigeria’s many ethnic and religious groups.