Zimbabwe's opposition leader was on the way to the airport when word came that assassins were awaiting him in his homeland Saturday, derailing plans for his return.

It was unclear when Morgan Tsvangirai would return to rally his party and campaign for the presidency against longtime leader Robert Mugabe.

The opposition and most observers say mounting violence and intimidation, mainly targeting opposition supporters, make it virtually impossible for a planned June 27 presidential runoff to be credible.

"We have received information from a credible source concerning a planned assassination attempt on President Tsvangirai today," spokesman George Sibotshiwe told The Associated Press. "Because of that it has been decided that the president will not return today."

Sibotshiwe said the information came as Tsvangirai drove from his home to his office in Johannesburg, and his next stop would have been the airport. He consulted with his own security and other party officials before deciding, reluctantly, not to go home.

Sibotshiwe would not identify the source other than to say he or she was in a position to know of the plot, which he said was striking in its detail. Sibotshiwe also refused to say whether Zimbabwean government officials were implicated in the plot, but he said the government had refused to address threats to Tsvangirai.

He said the opposition was working with regional leaders instead of the government to organize body guards and safe vehicles in Zimbabwe for its leader.

"It's almost impossible to work with the Zimbabwean government," Sibotshiwe said.

Repeated attempts Saturday to reach Zimbabwean police for comment were unsuccessful.

Tsvangirai had planned to address a party caucus in Harare, Zimbabwe's capital, on Saturday and a rally in Bulawayo on Sunday. Other party officials would lead those events, Sibotshiwe said.

Sibotshiwe said party officials would consult their own security experts and regional leaders for advice. He said Tsvangirai would return "at the earliest opportunity."

Tsvangirai has survived three assassination attempts, including one in 1997 by unidentified assailants who tried to throw him from a 10th floor office window. Last year, he was hospitalized after a brutal assault by police at a prayer rally, and images seen around the world of his bruised and swollen face have come to symbolize the plight of dissenters in Zimbabwe.

Tsvangirai's Movement for Democratic Change says that more than 30 of its supporters and activists have been killed since the first round of voting March 29, and that attacks are increasingly targeting its top leaders.

Tsvangirai won the first round, but, according to official results, fell short of an outright majority.

Tsvangirai claims he won the first round outright, but nonetheless agreed to take part in a runoff after the official results were announced May 2. He said, though, that the runoff should be held within three weeks of the announcement of results, as Zimbabwean law stipulates.

Instead, Zimbabwe electoral officials announced Friday the runoff would be June 27, eight weeks after the results were announced, prompting concern that Mugabe's force would use the time to orchestrate more attacks on opposition supporters.

Sibotshiwe said that despite escalating violence, the late runoff date and now the assassination threat, Tsvangirai would take part in the runoff. Continued...