South Africa ? 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.