Tensions boil over during tightly contested presidential and parliamentary elections that both sides say they are on track to win.
Five people have been killed in election-related violence in Ghana, casting a shadow over a country hailed for its stable democracy.
The deaths were reported as a flow of results confirmed the tight race for the presidency and Ghana's neighbours called for a peaceful outcome after the main camps traded barbs.
Since Monday's ballot, 21 "cases of electoral violence" have been recorded, six of them involving gunshots, the police said, giving a toll of five dead and 17 wounded.
The electoral commission published results from 11 out of the country's 16 regions, giving outgoing president Nana Akufo-Addo a narrow margin over opposition candidate John Mahama. Earlier, in results out of seven regions, it was Mahama who held a slight advantage.
The commission, which had been expected to give the results as early as Tuesday, said heavy rains that have pounded some regions had slowed the vote count, and urged the public to be patient.
Polling on Monday was viewed by observers as generally free and fair, but the political climate soured late Tuesday, when Mahama accused his rival of showing "credentials that are very undemocratic."
Akufo-Addo, he charged, had harnessed the military in a bid to sway the outcome.
"You cannot use the military to try and overturn some of the results in constituencies that we have won. We will resist any attempts to subvert the sovereign will of the Ghanaian people," the 62-year-old former president said.
Mahama made the accusations after rumours circulated on social media that he had conceded defeat.
Hours earlier, the presidency — releasing an unofficial tally — had claimed Akufo-Addo was ahead with 52.25 percent of the vote, against Mahama's 46.44 percent.
Information Minister Kojo Oppong Nkrumah told a press conference that allegations of intimidation by soldiers were false.
He also bluntly rejected Mahama's claim that his centre-left National Democratic Congress (NDC) had won a majority, of 140 seats, in the 275-member parliament.
We'll resist any attempts to subvert the will of the people. pic.twitter.com/c0W2EAsbfh— John Dramani Mahama (@JDMahama) December 8, 2020
"No candidates at this stage should undermine the work of the EC (electoral commission), it is irresponsible and it would endanger the peace of this country," Oppong Nkrumah warned.
The European Union's chief observer, Javier Nart, told a press conference on Wednesday that "Ghanaians voted freely."
"While there were isolated violent incidents, both on election day and during the campaign ... fears of violence and vigilantism fortunately didn't materialise: they were minor, isolated incidents, some of them tragic ones."
Akufo-Addo's centre-right New Patriotic Party (NPP) held a press conference, calling on supporters to rally in front of the president's residence in Accra.
Mahama and Akufo-Addo, 76, are old rivals who have faced off at the ballot box twice before.
Mahama was president for four years until 2016, before being succeeded by Akufo-Addo. Both of those elections were determined by small margins.
Despite the death toll and the heated accusations, Ghana has a history of electoral stability and grievances are typically pursued through the courts.
Akufo-Addo and Mahama on Friday signed a symbolic peace pact, which the 15-nation regional bloc ECOWAS urged "all political parties and their leadership to respect."
In a statement, the Economic Community of West African States said, "We appeal to political parties and their followers to refrain from any conduct that may undermine the successful conclusion of the electoral process."