A challenger who has lost three previous presidential polls took a comfortable lead after votes from more than half Zambia's constituencies were tallied Thursday, but unrest was reported among his supporters.
The last election was close, and this year's race between President Rupiah Banda and main opposition leader Michael Sata also was expected to be a tight race.
Two days after the vote, the Electoral Commission of Zambia said results were in from 85 of 150 constituencies by midday Thursday. Sata was leading with nearly 43 percent of the vote so far, or 693,787 votes. President Rupiah Banda has 36 percent, or 542,362 votes. Eight other candidates split the remaining votes.
Final results were expected by day's end.
Police Chief Francis Kabonde said small disturbances broke out and were quickly put down in impoverished urban areas in the southern Copperbelt province, Sata's stronghold. Sata's supporters have expressed fears of vote-rigging.
Sata's supporters have rioted after previous losses, and the violence following recent elections elsewhere in Africa is on some minds here.
With the atmosphere tense, the Electoral Commission of Zambia obtained a court order Wednesday barring media from reporting any but the confirmed results it was issuing.
Zambia's independent Civil Society Elections Coalition, which deployed some 9,000 observers across the country Tuesday, said Wednesday that despite some minor problems, the election had been "generally smooth and peaceful."
"The election, however, is not over," the coalition said. "Vigilance must continue to help ensure the credibility of the collation and announcement of results."
Banda seeks a new term after completing the term of his predecessor Levy Mwanawasa. Some analysts said Banda, who had been Mwanawasa's vice president, benefited from voter sympathy when he won by just 35,000 votes following Mwanawasa's sudden death in 2008.
During that 2008 special election, Zambia's economy was in trouble. Now, the country is benefiting from rising world copper prices. The boom has helped create 100,000 jobs in Zambia and the government has built bridges, airports and hospitals with revenue from copper.
While Banda is taking credit for the strong economy, the race is still expected to be close, in part because the ballot was crowded with challengers.