Mugabe has defied intense international pressure

Mr Boucher described the charge as "the latest example of a kind of retaliation against opposition and supporters that we're seeing under way in the aftermath of the election".

"We condemn this campaign of violence and intimidation," he said.

Mr Tsvangirai, who mounted a strong challenge to Robert Mugabe in last week's presidential ballot, was ordered to pay 1.5 million Zimbabwean dollars (about $27,000), and surrender deeds to property and his passport.

Mr Tsvangirai denies plotting to kill Mr Mugabe.

Sanctions

Last month Washington imposed a ban on travel to the US by Mr Mugabe and 19 of his top aides, in protest at the conduct of the elections.

	Commonwealth observers' findings High level of politically motivated violence and intimidation Zanu-PF's paramilitary youth group largely responsible for intimidation Restrictions on independent local observers Lack of transparency in the registration process Polling stations reduced in urban areas Many unable to vote in Harare and Chitungwiza because process was too slow Limitations on freedom of speech and movement hampered opposition campaign  Click here for observers' findings

Mr Boucher said further sanctions were being reviewed.

BBC Southern Africa correspondent Barnaby Phillips says the treason charge against Mr Tsvangirai destroys any immediate prospect of reconciliation between government and opposition.

Zimbabwe's Information Minister, Jonathan Moyo, said that nobody was above the law and Mr Tsvangirai had to answer the charges against him.

Wednesday saw a lukewarm response on the first day of a three-day general strike called by Zimbabwe trade unions - the first public test of opposition support since the election.

Police have declared the action illegal.

It was launched in protest at what the unions say is harassment of pro-opposition workers since the election.

The shadow lands and agriculture minister for Mr Tsvangirai's Movement for Democratic Change (MDC), Renson Gasela, was also charged with treason on Wednesday.

Mr Tsvangirai's deputy, Welshman Ncube, was charged and granted bail the day before the election, which Mr Mugabe officially won with 56% of the vote.

The three opposition politicians were ordered to appear in court on 30 April.

Commonwealth action

Australian Prime Minister John Howard - one of the leaders who announced Zimbabwe's suspension from the Commonwealth on Tuesday - had described the prosecution of the opposition leader as damaging to the process of reconciliation in the country.

And Mr Tsvangirai's lawyer, Eric Matinenga, described the court appearance as "continued harassment" and "a knee-jerk reaction to the events that unfolded yesterday in London".

Mr Tsvangirai's summons came after another Commonwealth leader, Nigeria's President Olusegun Obasanjo, told the BBC that the governing and opposition parties in Zimbabwe had agreed to discuss a plan put forward by the Commonwealth to resolve the political crisis.

Mr Obasanjo said this envisaged setting up a coalition government to promote reconciliation, with a new election to be held at an unspecified future date.

Secret video

The treason charge against Mr Tsvangirai carries a possible death penalty.

The MDC leader says the charges - based on a videotape which purports to show him discussing the assassination of Mr Mugabe with a political consultant - were fabricated to try to remove him from the political scene.

The allegations against Mr Tsvangirai were made by a Canadian political consultancy, Dickens and Madson, headed by former Israeli intelligence officer and Mugabe lobbyist Ari Ben-Menashe.

But there have been suggestions the videotape was heavily edited.