Opposition leader Morgan Tsvangirai beat President Robert Mugabe in Zimbabwe's presidential election on March 29, but not by a big enough margin to avoid a second round run-off.
The Zimbabwe Electoral Commission announced on Friday that Tsvangirai had won 47.9 percent and Mugabe 43.2 percent of the vote, news agencies reported.
"Since no candidate has received the majority of the valid vote cast... a second election shall be held on a date to be advised by the commission," Lovemore Sekeramayi, chief elections officer, was reported as saying by Agence France-Presse.
Reuters reported that Tsvangirai's Movement for Democratic Change (MDC), which has repeatedly said he won more than 50 percent of the vote, rejected the commission's figures.
The MDC said before the announcement of the result that Tsvangirai would not enter a run-off, but the Zimbabwe Independent reports from Harare that he will take part, notwithstanding public remarks to the contrary.