Welshman Ncube: Summoned by police

A party spokesman said they were General Secretary of the Movement for Democratic Change (MDC), Welshman Ncube, and MP Renson Gasela.

MDC leader Morgan Tsvangirai has already been charged with treason.

Mr Tsvangirai presents the main threat to President Mugabe in next month's election.

He said the charges, based on a videotape which purports to show him discussing the elimination of Mr Mugabe with a political consultant, were fabricated to try to remove him from the political scene.

The accusation would not stop him from standing in the poll, he added.

The opposition leader spent two hours on Monday being interrogated by police over the alleged treason plot - an offence punishable by death.

	Morgan Tsvangirai Organised strikes as leader of Zimbabwe Congress of Trade Unions Set up MDC in September 1999 Led MDC to win 57 seats in June 2000 elections Click here for a profile of Morgan Tsvangirai

He said the police had told him he would be summoned to appear in court at a later unspecified date.

The MDC leader added that he believed that police would not proceed with a prosecution before the election.

US State Department spokesman Richard Boucher said he was not aware of any evidence to back the allegations and said it appeared to be "another tragic example of President Mugabe's increasingly authoritarian rule".

Australia threatened to impose sanctions and to ask the Commonwealth to withdraw election monitors from Zimbabwe if Mr Tsvangirai was arrested.

But Zimbabwe's Home Affairs Minister, John Nkomo, told the BBC the case was a matter of following the law.

"President Mugabe is not a person who came up with that videotape and President Mugabe did not set up that meeting," he said.

"Morgan Tsvangirai has admitted that he did indeed hold those meetings and as far as President Mugabe is concerned, he would be interested in knowing Morgan Tsvangirai's side of the story."

The BBC's Hilary Andersson says the affair's implications for Zimbabwe's elections are very serious, as the political temperature is already heated and many Zimbabweans will see this as an attempt by the government to ensure its key opponent does not win.

Secret filming

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.

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Mr Ben-Menashe says he was approached by Mr Tsvangirai, who wanted Mr Mugabe "eliminated".

A meeting with Mr Tsvangirai last December was filmed, but the MDC leader denies discussing the assassination of Mr Mugabe.

An independent media monitoring group, the Mass Media Project of Zimbabwe, said the videotape at the centre of the allegations had been heavily edited and even rearranged.

Last year, charges of treason against Mr Tsvangirai were dropped after a court ruled them unconstitutional.