Police in the Zimbabwean capital, Harare, have intervened to prevent a planned demonstration in support of constitutional change and against Zimbabwe's involvement in the war in the Democratic Republic of Congo.

Several truckloads of riot police carrying shields and batons dispersed about a hundred demonstrators before the march could begin.

Busloads of people were turned away.

No reason was given.

The organiser of the march, Isaac Maposa, said the authorities in Zimbabwe were frightened of democracy.