Zimbabwe's opposition has called a general strike for next Tuesday after police banned a political rally planned for Sunday.
As tension increased over the election deadlock, police accused the opposition Movement for Democratic Change of "spoiling for a fight" and of deploying 350 youth wing members around the southern African country.
The police banned Sunday's MDC rally, which called an indefinite general strike starting next Tuesday to push for results from the March 29 election to be released.
State radio said Zimbabwe would be represented by three ministers at a summit this weekend of the Southern African Development Community (SADC), which was expected to place pressure on President Mugabe to release the results.
Human rights organizations and the MDC say Mugabe has unleashed a campaign of systematic violence in response to his ruling ZANU-PF party's first electoral defeat, when it lost control of parliament in the March 29 election.
The MDC says its leader, Morgan Tsvangirai, won a parallel presidential vote, whose results have not been announced, and have called on Mugabe to end his 28-year rule.
Tsvangirai told South African national radio from Botswana: "The situation in Zimbabwe is dire. The ... military has a rollout plan and is already embarking on intimidation, violence against the people."
Tsvangirai said he would be a "prime target."
The MDC accuses Mugabe of delaying the result so that he can intimidate opposition supporters before a runoff vote against Tsvangirai.
MDC spokesman Nelson Chamisa said the strike "starts Tuesday and goes on until the results are out."
Mugabe's decision not to attend the summit was a direct snub to Zambian President Levy Mwanawasa, the SADC chairman.
Mwanawasa last year described Zimbabwe as a "sinking Titanic" before getting back in line behind the body's relatively soft approach to Mugabe, who is still seen as a liberation-era hero to many Africans.
The absence of Mugabe, 84, from the summit is likely to reduce the chances of any action by SADC, already seen as largely toothless in face of the Zimbabwe crisis and overawed by the Zimbabwean leader.
State radio said demands for Mugabe to release the results were misplaced because that was the prerogative of the Zimbabwe Electoral Commission.
Zimbabwean police said all political rallies had been banned because officers were too busy guarding ballot boxes or deployed to prevent post-election violence.
An opposition source said Tsvangirai met President Thabo Mbeki of Zimbabwe's powerful neighbor South Africa yesterday to discuss the crisis. No details were revealed.
Tsvangirai earlier met African National Congress leader Jacob Zuma, who called for the results to be released.
"We urge all parties to respect the will of the people, regardless of the outcome," Zuma said in a speech on Thursday.
The White House said President George W. Bush had phoned African Union chairman and Tanzanian President Jakaya Kikwete to urge swift release of the results.
The Crisis in Zimbabwe Coalition, an alliance of 300 civic groups, warned that there was a growing threat of violence that would lead to mass atrocities in Zimbabwe if African leaders sat on their hands.
"If SADC leaders do not want blood on their hands, they must take action this weekend," coalition chairman Arnold Tsunga said in a statement.
Amnesty International and Human Rights Watch also have expressed concerns about the prospect of post-election violence.