LUSAKA (Reuters) - Zambia's ruling party presidential candidate Edgar Lungu took a slim lead over his rival Hakainde Hichilema after votes from more than half of constituencies were counted, the electoral commission said on Thursday.
With no reliable opinion polls in the southern African state, few experts are keen to call a winner in the contest to succeed Michael Sata, who died in office in October aged 77.
Results from 90 out of 150 constituencies showed Patriotic Front candidate Lungu, 58, had 50.75 percent of votes, compared to 45.14 percent for Hichilema, 52, a wealthy economist from the United Party for National Development.
Defence and justice minister Lungu polled 590,252 votes and Hichilema 524,976 out of just over 1.16 million ballots counted, the Electoral Commission of Zambia (ECZ) said.
Turnout was around 34 percent as heavy rains disrupted voting across much of the landlocked country. Observers said the election was conducted in a fair manner.
The final result was due to be announced on Friday but could be delayed.
ECZ chairperson Ireen Mambilima said the country's air force was helping deliver elections material from polling stations that could not be reached after heavy rains damaged some roads.
"I think if the Zambia Air Force will meet their target we are hopeful that we can finish tomorrow," she said on Thursday.
The kwacha was 1.9 percent stronger at 6.35 against the dollar at 1557 GMT, firming for the second day as the peaceful vote eased investor jitters about stability in Africa's second biggest copper producer.
With another election due late next year when Sata's term would have ended had he not died in office, the winner will have little time to turn around a stuttering economy in one of Africa's most promising frontier markets.
Zambia has averaged 6-7 percent growth as the mining sector boomed but that slowed to 5.5 percent last year, the International Monetary Fund says, and could ease further with the price of copper reaching a 6-year low this month.
Lungu, a former lawyer with a laid-back, populist style, has used his campaign to tap into the grassroots support of his predecessor Sata, promising voters cheaper food and fuel.
Hichilema, one of Zambia's wealthiest businessmen, has said if he wins he will draw on his experience in the private sector to attract foreign investment and diversify an economy, where copper accounts for 70 percent of export earnings.
(This story corrects tally of votes cast in paragraph 4)
Writing by Joe Brock; Editing by James Macharia