Zimbabwe's President Robert Mugabe threatened to arrest Morgan Tsvangirai, the opposition leader who faces Mugabe in a runoff election for president June 27, according to media reports released on Monday.

Mugabe issued the threat at a campaign rally in Kadoma, south of the capital of Harare, Reuters said on its website.

Opposition leader Morgan Tsvangirai has been repeatedly detained during his campaign, but has faced no charges. Tsvangirai's Movement for Democratic Change party says 66 people have been killed in the election violence by ruling ZANU-PF supporters.

Mugabe said the authorities were warning Tsvangirai and others opposition leaders that we will not hesitate to arrest them (for violence), and we will do that in broad daylight. They think they are protected by the British and the Americans. The law of the country has to be observed.

Official results of a disputed election March 29 showed Tsvangirai beat Mugabe, but not by enough votes to avoid a run-off, official results show.

Mugabe is battling to keep his 28-year hold on power in a country suffering economic collapse. His ZANU-PF lost control of parliament in the March election, but the president has the greatest say in running the country.

At another rally held on Sunday, Mugabe said appeared determined to keep a firm grip on the country's leadership.

We shed a lot of blood for this country. We are not going to give up our country for a mere X on a ballot, The Herald, Zimbabwe's government mouthpiece said.

How can a ballpoint pen fight with a gun? Mugabe said.