Results released Monday by the Independent National Electoral Commission (INEC) showed Buhari winning the state of Ekiti with about 57 percent of the vote.
Buhari also won a tight race in the state of Osun, defeating his main challenger Atiku Abubakar by a margin of about 10,000 votes.
More results are expected in the coming hours.
Voting took place Saturday in all of Nigeria’s 36 states and the federal capital territory, although INEC postponed the polls in some areas where voting was disrupted.
The Situation Room, an umbrella group of more than 70 civil society organization, says at least 39 people have been killed in election-related violence.
Despite the rescheduling of some elections, INEC said it was “generally satisfied” with the vote, the French Press Agency reported.
Political tensions were high last week as Nigerians prepared to elect a new president and parliament. During the campaign, Buhari’s All Progressives Congress and the main opposition Peoples Democratic Party accused each other of attempting to fix the outcome.
Last week, Buhari urged the military to be “ruthless” with anyone who tries to interfere in the voting process.The remark drew sharp criticism from Abubakar, who said the military has “no role to play” in the elections.
President Buhari was among the first of the country’s more than 72 million eligible voters to cast a ballot in his hometown of Daura when the polls opened Saturday for the country’s delayed election.
Nigeria’s elections were initially planned for February 16 but the electoral commission, citing logistical issues, abruptly postponed them just five hours before polling stations were set to open.
After ruling briefly as a military dictator in the 1980s, Buhari won the 2015 election, becoming the first opposition candidate to defeat a sitting president.