Zimbabwean President Robert Mugabe (R) and his South African counterpart, Thabo Mbeki, in Harare, 09 May 2008

South African President Thabo Mbeki is in Zimbabwe Friday to mediate an end to the country's political crisis.

South Africa's Foreign Ministry says Mr. Mbeki will meet political leaders in Zimbabwe, where violence has escalated since a disputed election in March.

Regional leaders have asked Mr. Mbeki to act as a mediator between Zimbabwe's ruling ZANU-PF party and the opposition Movement for Democratic Change.

But, the MDC says it does not want Mr. Mbeki as a mediator because the South African leader refuses to take a tough line with President Robert Mugabe.

On Thursday, a U.S. official, National Security Council spokesman Gordon Johndroe, called on Mr. Mugabe and his supporters to stop "violence and intimidation" against their political opponents. The MDC says 30 opposition activists have been killed since the March 29 election.

Zimbabwe's election commission said last week that MDC presidential candidate Morgan Tsvangirai fell short of a 50 percent majority in the election. It said Mr. Tsvangirai will have to contest a second round of voting against Mr. Mugabe.

The MDC insists that Mr. Tsvangirai won the first round of voting outright.

In another development, a Zimbabwean labor union says ZANU-PF militias have driven 40,000 farm workers from their land in recent weeks. The union says the militias are intimidating rural residents ahead of the next round of voting.

Zimbabwe's government denies launching a campaign of violence and accuses the MDC of carrying out its own attacks.

Some information for this report was provided by AFP, and Reuters.