Zimbabwe's government accused opposition leader Morgan Tsvangirai of treason, saying he and Britain are plotting to overthrow the president. Tsvangirai denounced the allegations as "outrageous." President Robert Mugabe's government lashed out at Tsvangirai by claiming he is plotting an "illegal regime change" - with former colonizer Britain's help - in accusations published in Zimbabwe's state-run newspaper. The paper cited a letter from Britain's prime minister, which the opposition says is a forgery. The British Embassy in Harare also denied it, saying "No such letter or wider correspondence exists." The accusation comes amid a government campaign of arrests, assaults and other intimidation designed to suppress political dissent following a March 29 vote that Mugabe is widely believed to have lost. Results from the presidential vote have not been released some three weeks after the ballot. Independent tallies suggest Tsvangirai won, but not with enough votes to avoid a runoff. The electoral commission says it cannot yet release results of the presidential vote because it is still verifying ballots and investigating anomalies.