The Movement for Democratic Change, the country's main opposition party, said last week it would demonstrate against the crumbling economy and call for a new constitution it said would guarantee that elections due in March were free and fair.

"We are proceeding with the march ... we're marching because our people are suffering ... there's no water, no electricity. The government is totally bereft and bankrupt of any capacity to govern this country. This government has failed," Tendai Biti, secretary-general of the Morgan Tsvangirai-led faction of the MDC, told reporters.

The police, who had initially allowed the march, said in a letter that they had banned the protest because the MDC had broken an agreement reached at a meeting last week.

Zimbabweans have tended to shy away from demonstrations, mainly from fear of a heavy-handed response by Mugabe's security forces.

Tsvangirai, who was arrested and beaten with dozens of opposition members while trying to hold an anti-government rally last year, said earlier this month the party might boycott the elections unless the government implemented a new constitution.