U.N. Secretary-General Ban Ki-moon urged Zimbabwean President Robert Mugabe on Monday not to hold the run-off presidential election as planned on Friday, saying the result would lack legitimacy.

Dutch officials said opposition leader Morgan Tsvangirai had taken refuge in the Dutch embassy in Harare after pulling out of the election because of attacks on his supporters.

Tsvangirai's Movement for Democratic Change said police raided its Harare headquarters on Monday and took away more than 60 victims of the violence sheltering there, including women and children. The MDC says nearly 90 of its supporters have been killed by militias backing Mugabe.

The Zimbabwe Electoral Commission said it was still looking forward to elections on Friday. "We don't have a war. We will be able to hold credible elections," ZEC chairman George Chiweshe said.

Ban, speaking to reporters at the United Nations after meeting the 15-nation U.N. Security Council, said Tsvangirai's decision to withdraw from the run-off was "understandable".

"I would strongly discourage the authorities from going ahead with the run-off on Friday," Ban said. "It will only deepen divisions within the country and produce a result that cannot be credible."

Ban said he was distressed by the events leading to Tsvangirai's withdrawal. "There has been too much violence and too much intimidation," he said. "A vote held in these conditions would lack all legitimacy."

Without specifically blaming Mugabe, Ban spoke of a "campaign of threat and intimidation" against the citizens of Zimbabwe, and said the situation was "the single greatest challenge to regional stability in southern Africa today."

The Dutch foreign ministry said Tsvangirai had not requested asylum but had spent Sunday night in the embassy after withdrawing from the June 27 election on Sunday. It said he was welcome to stay for his own security.

POLICE 'SHOCKED' BY REFUGE MOVE

Zimbabwean Police Commissioner-General Augustine Chihuri said the police had been 'shocked and surprised' by Tsvangirai's decision to seek refuge in the Dutch embassy.

".it is obviously a calculated move to besmirch the presidential run-off election due this Friday . and further brutalise the image of Zimbabwe and in particular the Zimbabwe Republic Police (ZRP) on the international arena," Chihuri told a news conference in Harare.

"We wonder from whom Mr Tsvangirai is running away or hiding," Chihuri said. The MDC leader said earlier this year there was a plot by the Mugabe government to kill him.

Announcing his withdrawal from the election on Sunday, Tsvangirai said his supporters would have risked their lives by voting, and said he was ready to negotiate with Mugabe's ZANU-PF party if the violence stopped.

Concern mounted both within and outside Africa over Zimbabwe's political and economic crisis, which has flooded neighbouring states with millions of refugees. Both the African Union and Southern African Development Community (SADC) were discussing the situation following Tsvangirai's pullout.

Former colonial power Britain said Mugabe must be declared an illegitimate leader and sanctions should be stiffened against his inner circle, which Prime Minister Gordon Brown called "a criminal and discredited cabal".

U.S. Secretary of State Condoleezza Rice said even if the run-off went ahead it would not legitimise Mugabe's government.

Several countries have urged a unity government to end Zimbabwe's dire crisis but both sides have previously rejected this. Analysts said Tsvangirai's withdrawal was likely to delay any solution of this kind.

Mugabe, 84, who has been in power since independence in 1980, has vowed never to hand over to the opposition, branding them puppets of the West.

He denies his supporters are responsible for the violence, which broke out after he and ZANU-PF lost elections on March 29. Official figures showed Tsvangirai fell short of an absolute majority in the presidential vote, forcing the run-off.

Mugabe has presided over a slide into economic chaos, including 80 percent unemployment and the world's highest inflation rate of at least 165,000 percent.

The African Union's top diplomat said he was consulting AU Chairman and Tanzanian President Jakaya Kikwete, the SADC and South African President Thabo Mbeki - the region's designated mediator on Zimbabwe - to see what could be done.

Jean Ping said the withdrawal and the political violence were "a matter of grave concern to the Commission of the AU".

SADC foreign ministers were discussing the Zimbabwe crisis in Luanda. Angolan Foreign Minister Joao Bernardo de Miranda was quoted by the state-run news agency ANGOP as saying the situation was extremely serious and Friday's vote would not be free and fair.

The Dutch government, a major aid donor to Zimbabwe, called on the United Nations, the European Union, the AU and neighbouring states to discuss new steps against Mugabe.