Zimbabwean police have fired tear gas at hundreds of opposition protesters on the streets of the capital, Harare, after a court banned a protest march.
The judge ruled an opposition stadium rally could go ahead but agreed with police warnings that a march would present a threat to public security.
Opposition leader Morgan Tsvangirai was detained for five hours then released ahead of the planned demonstrations.
He later accused the authorities of treating him like a "common criminal".
Mr Tsvangirai, who was arrested at his home in Harare early on Wednesday morning, addressed supporters at the rally site, Glamis Stadium, in the west of the capital.
He told a crowd: "If this is the reaction of this dictatorship, then the elections are a farce."
The Movement for Democratic Change (MDC) is demanding a new constitution before presidential and parliamentary polls that President Robert Mugabe said would be held in March.