A group of election observers on Thursday urged Ghanaians to trust the outcome of a presidential ballot lashed as "spurious" by the country's opposition.
President Nana Akufo-Addo, 76, won a second term with 51.59 percent of the vote, beating longtime rival John Mahama, 62, who garnered 47.36 percent, according to official results announced on Wednesday.
"The results declared by the electoral commission reflect how Ghanaians voted in the presidential election polls," Sheikh Arimiyawo Shaibu, from a coalition of election observers called CODEO, told a press conference in Accra.
The respected Ghanaian organisation urged the public to remain calm and for any disputes to be settled through legal channels.
The vote for the presidency took place on Monday at the same time as balloting for the 275-seat legislature.
The results of the parliamentary elections have not been announced and are expected to be very close between the two main parties.
Ghana stands out as a stable democracy in volatile West Africa, although tensions rose after Mahama claimed to have won a parliamentary majority and warned Akufo-Addo against stealing the vote.
The opposition rejected the presidential results after they were published late Wednesday.
"Overwhelming evidence available makes it impossible for us to accept this spurious and hurried conclusion," Haruna Iddrisu, an MP for the National Democratic Congress (NDC) party, told a press conference.
Speaking on behalf of the party, he said: "We intend to take decisive and concrete steps, both with the presidential and parliamentary results, to overturn this brazen and shameless attack on our democracy."
Mahama and Akufo-Addo are long-standing rivals.
This was their third bout against other, and in 2012, it was Akufo-Addo who contested Mahama's win.
CODEO -- the Coalition of Domestic Election Observers -- deployed observers to 4,000 out of 38,000 polling stations.
It appealed to Ghanaians to "remain calm, law-abiding and allow the system to work."
"We encourage any party or candidate with issues about the results to peacefully resolve these through proper legal and procedural channels," Shaibu said.
CODEO, set up by the Ghana Center for Democratic Development (CDD-Ghana) think tank, is drawn from civil society groups, faith organisation and professional bodies. It has been widely praised for non-partisan monitoring of elections.
Akufo-Addo, in a victory speech to supporters, said it was time "irrespective of political affiliations, to unite, join hands and stand shoulder to shoulder."
Observers, both Ghanaian and foreign, viewed polling as generally free and fair but police said five people were killed and 19 injured in election-related violence.