Early results from Zambia's presidential election were released on Saturday, with poll observers calling for calm as delays in the counting process followed a tense campaigning period.
President Edgar Lungu of the Patriotic Front (PF) and leading challenger Hakainde Hichilema were predicted to be in a close race for power as Zambia struggles with a weakening economy.
Hichilema, of the United Party for National Development (UPND), alleged on Friday that the count was being undermined by fraud.
The Electoral Commission rejected Hichilema's allegations that it was colluding with Lungu's party over the result, describing the charges as "regrettable".
By Saturday afternoon, partial results from 29 of the 156 constituencies put Lungu ahead on 262,149 votes with Hichilema on 243,799, according to the commission, with the other seven presidential candidates far behind.
Lungu took power only last year when he beat Hichilema by less than 28,000 votes in a snap election.
Zambia is known for its relative stability, but the run-up to Thursday's vote was marked by weeks of clashes between PF and UPND supporters, with at least three people killed.
The Christian Churches Monitoring Group, which had 1,670 observers at polling stations across the country, described the election as a "step backward for the country", expressing deep concern about the environment before the vote.
"We appeal to all Zambians, regardless of their affiliation to remain peaceful, to reject violence," the group said in a statement.
"Zambia is not a new democracy and should be a model to the region and beyond."
The CCMG report pointed to opposition candidates being unable to campaign freely, an impartial police force and unbalanced pro-Lungu media coverage.
An EU monitoring team also voiced concern about the violence in the run-up to the vote, which led to campaigning being suspended for 10 days -- a move which the observers said had hampered smaller parties running for office.
"The suspension of campaigning in districts of Lusaka and Namwala, southern province from 9-18 July... unduly affected small parties and independent candidates," EU Chief Observer Cecile Kashetu Kyenge told journalists.
The ruling party did not fully comply with the ban on campaigning, she added.
Estimated turnout was about 57 percent -- far higher than last year, with long queues and no major violence on voting day.
Zambia, in contrast to neighbours like Angola and Zimbabwe, has escaped war and serious upheaval in recent decades.
It last held a peaceful transfer of power to an opposition party in 2011 when Michael Sata took office.
Sata died in 2014, and the 2015 election gave Lungu the right to finish Sata's term.
Lungu's short term in office has been marked by the falling price of copper, the country's key export, with inflation rising to over 20 percent and unemployment soaring.
Constitutional changes mean that the winner must now secure more than 50 percent of the vote, leading to a possible second round run-off that would likely be held next month.
Hichilema, 54, a wealthy businessman who is making his fifth attempt to win the presidency, said when he voted that he would accept the election result if it was "free, fair and transparent".
On the campaign trail, the British-educated economist emphasised his business credentials as an asset to turning around the economy.
Known as "HH", he has major investments in ranching, property and healthcare in Zambia.
The former British colony, ruled by Kenneth Kaunda from 1964 until 1991, recorded GDP growth of 3.6 percent last year -- its slowest since 1998.
Growth was more than 10 percent in 2010.
Last year Lungu, 59, held a mass prayer gathering in the national stadium to ask for divine help to improve the economy.
About 60 percent of the population live below the poverty line, according to the World Bank.
The presidential, parliamentary and local election also included a constitutional referendum on amending the bill of rights. Full results of the vote were expected late Sunday.