March 29: Zimbabweans vote peacefully in presidential, parliamentary and local council elections.

April 2: Opposition Movement for Democratic Change says its own tallies show Tsvangirai won presidential elections outright with 50.3 percent of vote.

April 4: Ruling ZANU-PF party says there will be a runoff and endorses President Robert Mugabe as its candidate. Opposition goes to court to try to force release of all election results; court rejects demand.

May 2: Electoral Commission releases presidential results, saying Tsvangirai won most votes, but not enough to avoid runoff with Mugabe, the second-place finisher.

May 10: Tsvangirai, who left Zimbabwe after the election, announces in South Africa that he will participate in presidential runoff.

May 13: United Nations warns that postelection violence is nearing crisis levels, with several people killed, hundreds hospitalized and many more displaced by violence.

May 16: Electoral Commission sets runoff date as June 27, after moving the deadline to 90 days after official election results are released -- beyond the legally required 21 days.

May 17: Tsvangirai postpones return to Zimbabwe after his party said he learned about a planned assassination attempt.

May 24: Tsvangirai returns to Zimbabwe.

May 27: Tsvangirai says politically motivated violence has killed 50 of his supporters since the election.

June 3: Government orders international aid groups to suspend operations, after accusing them of campaigning for the opposition.

June 4: Tsvangirai detained for nine hours north of Bulawayo, Zimbabwe's second-largest city.

June 5: A mob believed loyal to Mugabe assaults a convoy of U.S. and British diplomats, beating a local staffer. The government orders aid groups to halt operations indefinitely.

June 6: Tsvangirai detained briefly while campaigning near Bulawayo.

June 12: Zimbabwe's No. 2 opposition official, MDC secretary-general Tendai Biti, arrested at Harare airport upon returning from South Africa. Tsvangirai detained by police twice briefly while campaigning in the south.

June 19: Biti formally charged with treason, which can carry the death penalty.

June 20: Zimbabwe Association of Doctors for Human Rights says it has recorded 85 deaths in political violence since the first round of voting.

June 22: Tsvangirai announces he is pulling out of the runoff, after thousands of ruling party militants blockade the site of the opposition's main election rally.