Lusaka - Zambia's ruling party candidate Edgar Lungu was Thursday leading in the race to replace the late president Michael Sata, authorities said as voting continued in parts of the country.
According to the Electoral Commission of Zambia, ballots from 80 of the 150 constituencies had been counted by late Thursday morning.
Lungu, the ruling Patriotic Front's candidate, was leading with 533 613 votes, closely followed by opposition leader Hakainde Hichilema of the United Party for National Development with 474 076.
"We have 80 constituencies which have been counted and verified," said electoral commission chair Irene Mambilima.
She said no discrepancies had been reported since counting began.
Voting was continuing at some 12 polling stations across the country after heavy rain disrupted the Tuesday election, forcing an extension.
Authorities said they had faced "unprecedented challenges" in delivering voting material to some remote areas in the copper-rich southern African nation.
Boats and ox-wagons had be deployed to get ballot papers to parts hit by torrential rains.
Also read: Zambia voters not deterred by heavy rains
Hichilema is seen as the main challenger to the PF's Lungu in the contest to replace Sata, who died in office last October of an undisclosed illness.
On Wednesday, police fired tear gas to disperse a group of Hichilema's supporters who had gathered outside a counting centre in the capital waiting for results.
Several people were arrested.
Hichilema, a wealthy businessman, cried fraud on the first day of voting, complaining about alleged acts of violence by ruling PF supporters and the extension of voting.
But the regional Southern African Development Community (SADC) mission has praised the vote as "reflecting the will of the people of Zambia", saying it was "peaceful, transparent, free and fair".
Election authorities were unable to give a date for the announcement of the final results.