Zimbabwe’s opposition leader Morgan Tsvangirai has taken refuge in the Dutch embassy in the capital, Harare.
A Dutch foreign ministry spokesman said Mr Tsvangirai had spent the night at the embassy as he feared for his safety but had not requested asylum.
On Sunday, he announced he was withdrawing from a presidential election run-off in the face of violence from ruling party militias.
Zimbabwean officials have said the second round will still go ahead.
But Botswana’s Foreign Minister Pando Skelemani said leaders of the Southern African Development Community (Sadc) would have to decide whether Zimbabwe could have a legitimate president in the current political climate.
“If in fact the atmosphere for an election is not free and fair you then can’t have someone having won,” he told the BBC.
“It would be the same as if you had been through the election and they are declared not free and fair, then you are back at square one.”
Ahead of a UN Security Council discussion about Zimbabwe, US Secretary of State Condoleezza Rice said President Robert Mugabe’s regime “cannot be considered legitimate in the absence of a run-off”.
Mr Tsvangirai says pressure from the UN and Sadc could force Mr Mugabe to give up power.
“My assessment is that if there is a collective position by all Sadc leaders, that would be sufficient pressure—that voice is essential,” he told US National Public Radio.
“The conditions of the Security Council on Zimbabwe has one outcome that we will expect . . . to appoint a mission to investigate the level of abuses that have taken place—rape, torture, murder—and the various human rights abuse that has taken place.”
Former UN Secretary General Kofi Annan told the BBC that he believed the elections should be postponed:
“Honestly, given what has happened, I doubt that anyone would accept the results, so they should put off the elections. But I think it is important that we all realise that Zimbabwe needs our help.”
Zimbabwe’s Justice Minister Patrick Chinamasa said Mr Tsvangirai’s announcement of his withdrawal was a ruse as he had not sent a formal notice yet.
The BBC’s Peter Biles in Johannesburg says Mr Tsvangirai is now considering his next move, but he remains in the Dutch compound.
Dutch Foreign Minister Maxime Verhagen said that if Mr Tsvangirai was looking for safety at the diplomatic mission, he was welcome.
“We’ve seen the last weeks a new low in the tortured history of Zimbabwe and I think that Mr Mugabe no longer has any moral legitimacy in the eyes of the people of Zimbabwe,” she told the BBC.
Mr Tsvangirai blames supporters of President Mugabe and the ruling Zanu-PF party for the death of 86 of his supporters in the run-up to the second-round, due to be held on Friday.
On Monday, more than 60 supporters of Mr Tsvangirai’s Movement for Democratic Change (MDC) party were arrested at its Harare headquarters.
MDC spokesman Nelson Chamisa said those arrested were women and children who had fled political violence.
Zimbabwean police told AFP news agency they had only moved 39 people from the building for “hygiene reasons”.
President Mugabe and Zanu-PF blame the opposition for political violence across the country.
The MDC won the parliamentary vote in March, and claims to have won the first round of the presidential contest outright.
In the official results, Mr Tsvangirai led but failed to gain enough votes to avoid a run-off.