Morgan Tsvangirai speaks at Liberal International Congress in Belfast, Northern Ireland, 16 May 2008

The leader of Zimbabwe's opposition party will not return home as scheduled Saturday because of security concerns.

A spokesman for the Movement for Democratic Change says it has received information from a "credible source" about an assassination plot against Morgan Tsvangirai.

Mr. Tsvangirai has been out of Zimbabwe since the March 29 presidential and parliamentary elections. Official results show him beating President Robert Mugabe, but falling short of the majority needed to avoid a runoff election.

The MDC leader was expected to return from Europe and begin campaigning for the second round vote, which has been scheduled for June 27.

The party has scheduled a large rally for Sunday.

The MDC and human rights groups say Mr. Mugabe's supporters are conducting a terror campaign against the president's political opponents. The party says more than 30 of its activists have been killed since the first round of voting on March 29.

Mr. Tsvangirai said Friday that election violence must stop or the runoff vote will not be legitimate.

Mr. Mugabe's ruling ZANU-PF party and government officials reject the allegations and accuse the MDC of fomenting the violence.

The president told his supporters Friday the March elections were "disastrous" for him, but he is vowing to win the runoff vote.

Mr. Mugabe has led Zimbabwe since the country won independence in 1980. The MDC has accused him and his party of manipulating the election results to hang onto power.

The president says his opponents want to remove him from office and are backed by Western countries led by former colonial power, Britain.

Some information for this report was provided by and Reuters.