Zambian opposition supporters rioted Thursday in two mining towns, complaining that results for a tight presidential election were too slow to come two days after the vote, police said.

"We are trying to handle the situation. We have riots in Kitwe and Ndola," regional police chief Martin Malama told AFP.

Spontaneous riots erupted in the Copperbelt towns of Kitwe and Ndola, in northern Zambia, as demonstrators stoned cars and government buildings, according to police.

In Kitwe, angry protesters set alight a market in town.

President Rupiah Banda and opposition leader Michael Sata were locked in a tight race for president that was marred by rioting on election day.

The latest results put Sata ahead with 47 per cent of the vote to Banda's 34 per cent, with 33 of the country's 150 constituencies reporting.