Zimbabwe's government has accused opposition leader Morgan Tsvangirai of treason, saying he plotted with former colonial power Britain to force regime change in recent elections.

Morgan Tsvangirai addresses a press conference in Harare, 05 Apr 2008

Both Britain and the opposition Movement for Democratic Change quickly denied the allegations.  In a statement, the British embassy in Zimbabwe said an alleged letter to MDC leader Morgan Tsvangirai from British Prime Minister Gordon Brown is a forgery.

Zimbabwe's state-run Herald newspaper Thursday said Mr. Tsvangirai had approached Britain about using force to topple President Robert Mugabe.

Mr. Brown said Wednesday that no one believes Robert Mugabe won the March 29 presidential election.

Thursday, South Africa's government, the European Commission and the Group of Eight industrialized nations joined other world powers in urging the quick release of the election results.

South Africa's statement marked the first time the country has officially called for the release of the results.

The country's president, Thabo Mbeki, has been widely criticized for saying there is "no crisis" in Zimbabwe.

Zimbabwe's opposition Movement for Democratic Change says its candidate, Morgan Tsvangirai, defeated President Mugabe in the presidential election.  Independent monitors say Mr. Tsvangirai finished on top in the election but may have fallen short of the majority needed to avoid a run-off.  No official results have been released.

The opposition and human rights groups have accused the government of using militias to intimidate MDC supporters ahead of a possible run-off.

The U.S. embassy in Harare Thursday said it has "disturbing and confirmed" reports of threats, beatings, abductions and even murders in rural communities that generally support the opposition.

Some information for this report was provided by AFP and Reuters.