Zimbabwean opposition leader Morgan Tsvangirai will not return home on Saturday as expected to prepare for the second round of elections against Robert Mugabe, his party said.

Tsvangirai has been out of Zimbabwe for over a month and had been due to return from Europe on Saturday to campaign for the June 27 run-off. He beat Mugabe in the first round on March 29, but not by enough votes to avoid a second round.

"We can't say why he will not be coming today, except to say it's due to circumstances beyond our control," said Movement for Democratic Change party spokesman Nelson Chamisa.

Chamisa said an MDC rally scheduled in Zimbabwe's second city of Bulawayo on Sunday would go ahead, but would not say whether Tsvangirai would be back in the country in time to address it. He has been out of the country since April 8.

The opposition scored a small victory on Friday when a court ordered police not to interfere with the rally, which the force had banned.

The March elections were followed by widespread violence, which the MDC says left at least 40 of its supporters dead and scores of others injured. Mugabe's ruling ZANU-PF party says the opposition has driven the post-vote violence.