Nairobi/Accra - Ghana's opposition candidate has taken an slight early lead in the run-off presidential election, Ghanaian media said Monday.

John Atta Mills of the National Democratic Congress (NDC) has 50.89 per cent of the vote, compared to 49.11 per cent for Nana Akufo-Addo of the ruling New Patriotic Party (NPP), Joy Radio said on its website.

The partial results are based on 171 of 230 constituencies.

The electoral commission is expected to release full results by Tuesday afternoon at the latest.

While Sunday's election passed off peacefully, the two parties accused each other of attempting to rig the vote.

The NDC said its officials were intimidated and harassed. The NPP countered with claims that its polling agents were harassed by the NDC. There were also reports of attempted ballot box theft.

US envoy to Africa Jendayi Frazer called on both parties not to raise tensions by spreading rumours.

"Some of the statements by the political parties` officials have been irresponsible and there are a number of rumours that have been going on that are being repeated by some of the radio stations that are associated with the parties," the BBC reported her as saying.

The run-off came after neither man was able to score a decisive victory in the first round in early December.

The election is seen as key to African democracy, which sorely needs a boost after electoral chaos in Kenya and Zimbabwe and coups in Mauritania and Guinea this year.

Foreign election monitoring teams are in place to observe the election. The EU's election monitoring team, which hailed the first round as a a credit to democracy, is due to deliver its verdict on the second round on Tuesday.

Atta Mills and Akufo-Addo are vying to replace John Kufuor, who must step down in January after serving two terms.

Neither candidate is expected to institute major policy changes and both have promised good governance of revenue from newly discovered oil, due to come onstream in late 2010.

Ghana's National Petroleum Corporation expects 120,000 barrels per day initially, with that figure rising to 250,000 barrels a day within two years.

Ghana is the second-largest cocoa grower in the world and Africa's second-biggest gold producer, yet there is still widespread poverty among ordinary Ghanaians. (dpa)