Ghana's ruling New Patriotic Party candidate, Vice President Mahamudu Bawumia, on Sunday conceded defeat in the country's presidential election after failing to shake off widespread frustration over the struggling economy.

Defeat in Saturday's election ended two terms in power for the NPP under President Nana Akufo-Addo, marked by Ghana's worst economic crisis in years, high inflation and a debt default.

"The people of Ghana have spoken, the people have voted for change at this time and we respect it with all humility," Bawumia said in a news conference.

Bawumia said he had called his opponent, National Democratic Congress (NDC) candidate and former president John Mahama, to congratulate him.

Blaring horns and cheering, Mahama supporters were already gathering and celebrating outside the party campaign headquarters in Accra.

On his X account, Mahama confirmed he had received Bawumia's congratulatory call over his "emphatic victory."

The vice president said Mahama won the presidency "decisively" as well as Mahama's NDC party winning the country's parliament election, according the NPP's own internal tally of votes.

Ghana's economic woes dominated the election, after the west Africa gold and cacao producer went through a crisis of default and currency devaluation, ending with a $3 billion International Monetary Fud bailout.

Earlier, NDC spokesperson Sammy Gyamfi told reporters the party's internal review of results showed Mahama won 56.3% of the vote against 41.3% for Bawumia.

"It is very clear the people of this country have voted for change," Gyamfi said.

Political parties had agents at polling stations to observe and tally the initial vote counts before the ballots were sent for official collation by the election commission.

Earlier, Commission Deputy Commissioner Bossman Asare told reporters regional results had yet to arrive at the national center.

The commission had said official results were likely due by Tuesday.

With a history of democratic stability, Ghana's two main parties, the NPP and NDC, have alternated in power equally since the return to multiparty politics in 1992.

Under the slogan "Break the 8" -- a reference to two terms in power -- Bawumia had sought to lead the NPP to an unprecedented third term. But he struggled to break away from criticism of Akufo-Addo's economic record.

Though inflation slowed from more than 50% to around 23%, and other macro-economic indicators are stabilizing, economic struggles were still a clear election issue for many.

That frustration opened the way for a comeback challenge from Mahama, who was president from 2012 to 2017 but since failed twice in presidential bids.