LUSAKA - Zambia's election commission will on Thursday begin verifying ballots cast in last week's controversial presidential vote to enable the opposition to challenge the result in court, officials said on Wednesday.

"We start our verification tomorrow (Thursday) and this is to check all election materials, what was used and what has remained," Electoral Commission of Zambia (ECZ) spokesman Chris Akufuna told Reuters.

Under Zambian law, the verification of ballots is required before an aggrieved politician can ask the court to demand all ballots are recounted.

Defeated Patriotic Front (PF) leader Michael Sata has branded the election to find a successor to late president Levy Mwanawasa a fraud, and said he planned to apply to the court for a recount.

Mwanawasa died from a stroke in August, two years into his second five-year presidential term.

Sata, who says the poll was marked by discrepancies between vote tallies and the number of voters on registration lists, led through two days of counting before Rupiah Banda overtook him as the last results were counted.

Banda was sworn in as president on Sunday.

PF chairman for local government Winter Kabimba said the electoral commission had called for the verification after the party demanded it be done to facilitate its legal challenge.

"Initially we had asked for verification in only 38 constituencies, but now we want verification in all 150 constituencies and we have hence dispatched our election agents to all the polling districts across the country," Kabimba told Reuters.

Kabimba said the PF would launch its legal challenge to recount all votes once the verification exercise was complete.

"This verification is like an audit to determine all ballots that were delivered to polling stations and those that were actually used. After that we will demand that the court orders a vote recount to see how many votes each of the candidates received," he said.