Zambian ruling party candidate Mr Levy Mwanawasa has taken an early lead while the opposition complained over the trickle of results from the country's closest presidential race since independence.
The latest certified results from the Electoral Commission, for 23 of 150 constituencies, gave 92,049 votes to Mr Mwanawasa, President Frederick Chiluba's chosen heir, against 80,792 for Mr Anderson Mazoka.
The Commission only released figures for the two top candidates. Mr Christon Tembo, the only other man deemed to have a realistic chance, appeared to have slipped far behind.
Mr Tembo of the Forum for Democracy and Development (FDD), said he could not believe predictions that the government had done well in the northern and Copperbelt provinces, and reiterated claims of vote-rigging.
Zambians confounded predictions of a low turnout due to the Christmas holidays and seasonal rains by queuing for as long as 10 hours to cast their ballots on Thursday. Some polling stations stayed open until mid-morning yesterday to accommodate the turnout, which the electoral commission estimated at 80 per cent.
Analysts saw the surprise rush as a possible sign of voter frustration with the MMD party, under which the economy has stagnated and corruption increased since it came to power in 1991.
Zambia also has a huge HIV/AIDS problem, although only one candidate used it as an election issue.