By Alastair Leithead BBC correspondent in Johannesburg

The leader of the opposition in Zimbabwe, Morgan Tsvangirai, has appeared in court with two other high-ranking party officials charged with treason.

But the case has again been postponed, this time until August.

I don't know what's going on here

Morgan Tsvangirai, opposition leader

Mr Tsvangirai, leader of the Movement for Democratic Change, and colleagues Welshman Ncube and Renson Gasela have been accused of plotting to assassinate President Robert Mugabe.

Walking out of the courtroom, Mr Tsvangirai described the five minute hearing as "a circus".

"I don't know what's going on here," he said.

He and his co-accused deny charges of treason over allegations they plotted to assassinate President Mugabe.

'A set-up'

They argue they were set up by government agents trying to discredit Mr Tsvangirai in the lead-up to the March presidential election.

President Mugabe won elections said to be flawed

President Mugabe won the election, but the result was described as severely flawed by the international community, and rejected by the opposition.

The case has been remanded until 2 August, after the judge accepted the prosecutor's request for another delay.

The state now has three months to decide whether to indict the men for trial in the High Court if convicted they face the death penalty.

The charges have been condemned by western countries as a form of political retribution, an accusation the government denies.

Mr Tsvangirai was released on bail after being formally charged with treason in March.

He was ordered to pay 1.5 million Zimbabwean dollars (around $27,000), and surrender deeds to property and his passport.

Commonwealth observers said the presidential election in March was marred by a climate of fear and violence against opposition supporters.

As a result Zimbabwe was suspended from the Commonwealth for a year.