Zimbabwe opposition leader Morgan Tsvangirai withdrew on Sunday from the June 27 presidential run-off election, citing political violence and an unfair poll that would favor President Robert Mugabe.

?We in the MDC (Movement for Democratic Change) have resolved that we will no longer participate in this violent, illegitimate sham of an election process,? he told reporters in Harare, before urging the United Nations and African Union to intervene to prevent a ?genocide?. Zimbabwe?s opposition MDC hopes its withdrawal from the June 27 presidential run-off election will prompt ?more serious action? from the United Nations, African Union and regional body SADC, a MDC official said on condition of anonymity.

Tsvangirai announced his decision during a news conference in Zimbabwe?s capital after thousands of ruling party militants blockaded the site of the opposition?s main campaign rally. «Conditions as of today do not permit the holding of a credible poll,» Tsvangirai said. «Given the totality of these circumstances, we believe a credible election is impossible. We can?t ask the people to cast their vote on June 27 when that vote will cost their lives. We will no longer participate in this violent sham of an election.»

South Africa on Sunday urged Zimbabwe?s opposition to continue with talks to find a solution to the political problems in Zimbabwe after MDC leader Morgan Tsvangirai pulled out of a June 27 presidential run-off election.?We are very encouraged that Mr. Tsvangirai, himself, says he is not closing the door completely on negotiations,? said Mukoni Ratshitanga, spokesman for South African President Thabo Mbeki, who is mediating between Zimbabwe?s opposition and President Robert Mugabe.Zimbabwe?s opposition.

Journalists beaten

The MDC earlier said that youth militia loyal to Mugabe attacked an MDC rally in Harare, beating journalists and forcing election observers to flee. ?Thousands of ZANU-PF youth militia, armed with iron bars, sticks and other weapons, have attacked journalists and forced election observer teams to flee from the venue of the MDC scheduled rally. Police are firing tear gas,? the MDC said in a statement.

Tsvangirai, who beat Mugabe in a March 29 vote but failed to win the absolute majority needed to avoid a second ballot, has already been detained by police five times while campaigning and he says at least 70 MDC members have been murdered. A spokesman said on Friday that he was considering withdrawing from the election because of the campaign of physical intimidation against opponents and voters.

It was not clear whether Tsvangirai himself had arrived at the rally when the violence apparently erupted. Police had banned the rally, which was to be the highlight of Tsvangirai?s stormy election campaign. A High Court in Harare on Saturday overturned the police ban.

Tsvangirai said he won the March vote outright and only relunctantly agreed to a run-off. The state-run media has refused to run the opposition?s political ads and police have blocked some of its rallies. Tendai Biti, a top MDC official and lieutenant to Tsvangirai, is in custody on a treason charge and other offences that carry a possible death penalty. A magistrate has ordered him held until at least July 7.

Mugabe has repeatedly vowed never to turn over power to the opposition, which he brands a puppet of Britain and the United States. Mugabe, 84, is fighting to cling onto power in the country he has ruled since independence from Britain in 1980. Once prosperous, its economy is now ruined and millions have fled the political and economic crisis to neighbouring states. He has blamed the political violence on the opposition and denies security forces were responsible for brutality.

There is, however, growing pressure on his government to put an end to the violence. A growing chorus of African leaders added their voices this week to concerns that the election will be illegitimate. Angolan President Jose Eduardo dos Santos, a longtime Mugabe ally, on Friday urged the Zimbabwean leader to allow the election to proceed in a spirit of tolerance and with respect to democratic norms.

■ Tsvangirai is a former union leader who has been a thorn in Mugabe?s side for a decade as the head of the Movement for Democratic Change (MDC), the main opposition group.

■ The son of a bricklayer, Tsvangirai was born in 1952 in central Zimbabwe.

■ He worked in a mine to feed his family and cut his political teeth in the labour movement as a mine foreman.

■ Tsvangirai helped found the MDC in 1999. Despite intimidation, it stunned the ruling party by winning 57 of 120 seats in a 2000 parliamentary vote.

■ Tsvangirai was acquitted of plotting to assassinate Mugabe and seize power before a 2002 presidential election.

■ Mugabe?s party won a crushing majority in a 2005 parliamentary election, which the MDC said was rigged.

■ The MDC split in 2005 in a feud over how to tackle Mugabe. A splinter group accused Tsvangirai of behaving in a dictatorial fashion.

■ Tsvangirai was arrested at an anti-Mugabe rally in 2007. He said he had been attacked at a police station. Critics said the incident helped revive his sagging political fortunes.

■ The second round follows the disputed 2008 presidential election in which official results showed Tsvangirai beat Mugabe, but not by enough votes to avoid a run-off.