Nigeria's President Muhammadu Buhari reelected, but opponent rejects results

Buhari, who first came to power in 2015 after defeating then-incumbent Goodluck Jonathan, led his main challenger Atiku Abubakar with 1.7m votes in results announced by the Independent Electoral Commission (INEC), in Abuja, Nigeria's capital.

Buhari of the All Progressives Congress (APC) claimed 15,191,847 (56%) while Abubakar received 11,262,978 (41%) of votes in the weekend election, according to the commission, which finished counting state-by-state results on Tuesday.

Abubakar's People's Democratic Party rejected the results and called for fresh elections in some parts of the country where they allege over-voting and other irregularities.

"We demand the immediate and outright cancellation of presidential election results in Yobe, Zamfara, Nasarawa and Borno states as submitted by INEC presiding officers and ask for the conduct of fresh elections in these states," PDP spokesman Tanimu Turaki said.

At least 39 people were killed in election-related violence, according to the Situation Room, a coalition of more than 70 civic organizations that monitored the elections.

The Situation Room, citing data from analysis firm SBM Intelligence, said most of the deaths occurred in the southern oil-rich Rivers state where seven people were killed in clashes between the Nigerian Army and armed men.

But despite the violence, US observers from the International Republican Institute and the National Democratic Institute (IRI/NDI) said that although the deaths were tragic, they should be placed in the broader context.

"We don't want to overemphasize the deaths," the IRI's John Tomaszewski told CNN Monday.

"We understand the contextual relationship. Violence happens every day here. It's not just on Election Day."

The death toll reported in the presidential vote is lower than in previous national elections. The International Crisis Group said at least 100 people were killed in violence that broke out during and after the 2015 election and Human Rights Watch reported 800 killed in the post-election violence of 2011.