Zimbabwe's government has ignored a significant call from South Africa to release the result of the presidential elections and has accused the opposition leader, Morgan Tsvangirai, of treason by plotting with Britain to overthrow the President, Robert Mugabe.
Themba Maseko, a South African government spokesman, said the situation in Zimbabwe was "dire". Mr Maseko said: "When elections are held and results are not released two weeks after, it is obviously of great concern."
The comments mark a significant shift from South African President Thabo Mbeki's policy towards Mr Mugabe's regime, which has has divided his own party, the ANC, and attracted stinging criticism.
But South Africa confirmed that it will not intervene to stop a shipment of Chinese-made weapons from reaching Zimbabwe, despite fears of a violent crackdown in the country.
A Chinese ship docked in Durban harbour late on Wednesday carrying three million rounds of ammunition for small arms, 3,500 mortar bombs and mortar tubes, as well as 1,500 rocket-propelled grenades, according to local media.
Mr Maseko said that as long as the administrative papers are in order, South Africa cannot intervene to prevent weapons being transported through its territory to its landlocked neighbour. "We are not in a position to act unilaterally to prevent a trade deal between two countries. South Africa is not at all involved in the arrangement. It would be possible but very difficult for South Africa to start intervening and saying that we will not allow the shipment through."
Mr Mbeki used his nation's current presidency of the UN Security Council to prevent calls by Britain and others for Zimbabwe to be put on the council agenda on Wednesday. Afterwards, he admitted there were "things that have gone wrong" in Zimbabwe, and said opposition parties must be able to participate in verifying poll results.
Mr Tsvangirai, the leader of the Movement for Democratic Change (MDC), called the treason charge "outrageous" and said the 84-year-old Mr Mugabe, who has led Zimbabwe since independence from Britain 28 years ago today, might be forced to "face justice".
The treason claim against the MDC leader, which recalls past court battles on the same charge, arose after Harare's state-owned Herald newspaper published what purported to be a letter by Mr Tsvangirai begging for British military intervention, and a reply from Gordon Brown.
The British embassy denounced the alleged letter from the Prime Minister as a "forgery", saying: "No such letter or wider correspondence exists." But Zimbabwe's Justice Minister, Patrick Chinamasa, said the opposition leader had behaved "treasonably", and there was no doubting the consequences.
The affair follows a familiar pattern: Mr Tsvangirai has twice before been charged with treason, which carries the death penalty. The last case tied down the MDC leader for 18 months, defending himself after the government produced a videotape which appeared to show him trying to buy arms for an insurrection.
Mr Tsvangirai has remained abroad most of the time since the 29 March election, in which the ruling Zanu-PF party lost its parliamentary majority and Mr Mugabe is believed to have been beaten in the first round, according to independent monitoring groups. Yesterday, he told the Associated Press Mr Mugabe was losing the chance of an "honourable exit".
"The more he is digging in, the more he's abusing people," he went on. "I still think we should forgive and forget. But given the wave of violence against the people, how do you sell that to the people?" The MDC leader has said that he was not interested in a "witch hunt" because it would distract from mending the political and economic crises.
Opponents fear the President and his associates would simply cling to power all the harder if they face being tried for human rights abuses.
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