Zimbabwe's opposition has rejected results that give it the most votes in the country's presidential election, but not enough to avoid a run-off.
The Movement for Democratic Change said it had been cheated of thousands of votes that would have given candidate Morgan Tsvangirai an outright victory.
But MDC leaders did not rule out taking part in a second round, saying they would decide the issue this weekend.
Not participating would hand automatic victory to President Robert Mugabe.
Mr Mugabe has accepted the long-awaited results that gave him 43.2% of the vote, compared with 47.9% for the MDC candidate Morgan Tsvangirai.
A spokesman for Mr Mugabe said he would stand in a second round of voting.
'Campaign of violence'
The BBC's Peter Biles in Johannesburg says although the result of the March 29 election is inconclusive, it represents a humiliation for the 84-year-old president.
MDC Secretary General Tendai Biti said Mr Tsvangirai should be declared president, as he had gained 50.3% of the vote.
"Morgan Tsvangirai is the president of the republic of Zimbabwe to the extent that he won the highest number of votes," Mr Biti said.
Mr Tsvangirai should be allowed to lead a government of "national healing" that included members of Mr Mugabe's Zanu-PF party, he said.
The Zimbabwe Electoral Commission (ZEC) said a run-off should be held within three weeks, and a date would be announced later.
The MDC says that as well as rigging the vote, ruling party supporters launched a campaign of intimidation and violence in rural areas following the elections.
It says the delay in announcing the results served to give pro-government militants time to organise and carry out their attacks in anticipation of a run-off.
The MDC says hundreds of people have fled their homes and 20 have been killed.
Zanu-PF party says the scale of the violence has been exaggerated, and accuses the MDC of staging its own attacks.
International concerns
Former Finance Minister Simba Makoni, who came third with 8.3%, drops out of the race.
He declined to endorse either candidate after the results were given, saying political leaders should work together and avoid another round of voting.
The US, the EU and the UK all questioned whether a run-off could be fair.
"For any second round of the presidential election to be considered free and fair ... an end of violence as well as the presence of international observers is of crucial importance," said a statement from the current holder of the EU presidency, Slovenia.
US state department spokesman Tom Casey said the final tally had "rather serious credibility problems given the inexplicably long delays and some of the post-election irregularities".
And British Foreign Secretary David Miliband said: "Any second round must be free, fair and open to international monitors. We will continue to support those working for democracy in Zimbabwe and regional and international partners committed to change."
Source: MJFM
