Lusaka, Zambia - The results of Zambia's presidential by- election were trickling in Friday, showing opposition leader Michael Sata polling well in his strongholds in the capital Lusaka and the Copperbelt mining region.

Results from 16 constituencies in the Copperbelt showed him leading acting president Rupiah Banda by around two votes to one.

Sata had also taken two constituencies in Lusaka region, including Lusaka Central, while Banda had won two constituencies in his home region of Eastern Province.

With only around 20 of a total 150 constituencies announced, it was too early to call the election for either candidate. The final results could take several days.

Thursday's election to choose a successor to ex-leader Levy Mwanawasa, who died in August following a massive stroke, passed off peacefully, but Zambians are still holding their breath in anticipation of possible violence, given threats by Sata not to accept the poll outcome if he loses.

Sata has accused the police and army of being in cahoots with the Electoral Commission of Zambia to produce a win for the ruling Movement for Multi-Party Democracy (MMD).

Sata has also complained about the electronic transfer of results from constituencies to the election centre in Lusaka, arguing the method is open to manipulation and demanding in a letter to the electoral commission Thursday that the results be transferred manually. The commission has ignored the call so far.

Although two other candidates were running, the election came down to a two-horse race between longtime diplomat Banda, 71, and Sata, a former government minister, who was defeated both in 2001 and 2006 by Mwanawasa and is also 71.

Voter turnout was expected to be lower than the 2006 election, which registered more than 70-per-cent participation.

Sata's initial refusal in 2006 to accept defeat - he accused the state of rigging - sparked days of rioting that ended only when the army was deployed.

Sata has promised to cut taxes and give Zambians a greater stake in mining companies and para-statals.

Banda has campaigned on a theme of continuity with Mwanawasa's prudent economic policies, which won over foreign investors, particularly Chinese investors, who have ploughed around half a billion dollars into Zambia, mostly into mining.

The economy has weighed heavily on the election. Copper prices are plummeting as slower global growth depresses demand for commodities.

Despite strong growth in recent years, Zambia is ranked among the poorest countries in the world, where about 65 per cent of its people live on less than a dollar a day. (dpa)