Harare: Riot police raided the headquarters of Zimbabwe's main opposition party on Friday and detained scores of people, officials said.

At least 100 supporters of the Movement for Democratic Change were bundled into a crowded police bus before taken away, a witness said.

"They took everyone in the building, including those who had come just to seek medical care," said MDC spokesman Nelson Chamisa.

Police said the raid targeted people who had sought refuge at the opposition headquarters after having "committed crimes" outside Harare.

MDC claims it defeated President Robert Mugabe in the March 29 elections. The delay to the presidential poll result has stoked fears of more violence in the country.