Zimbabweans began voting on Saturday in a referendum expected to adopt a new constitution that would clip presidential powers and lead to an election that will decide whether Robert Mugabe extends his three-decade rule.
Mugabe's ZANU-PF party and the Movement for Democratic Change (MDC) of his rival Prime Minister Morgan Tsvangirai are supporting the draft charter, making the vote almost a rubber stamp exercise.
Polling stations opened shortly after 0500 GMT. In Mbare, the oldest township in the capital that has witnessed clashes between ZANU-PF and MDC supporters in the past, more than 100 people filed patiently into a polling station.
Results are expected within five days.
A new constitution is a prerequisite for the next presidential and parliamentary elections, expected later this year under a power-sharing deal signed by Mugabe and Tsvangirai in 2008 after violent and disputed elections.
The run-up to the referendum has so far been peaceful but the vote is seen as a dry run for the general elections later this year, where ZANU-PF is expected to face a stiff challenge from the MDC, although there are no reliable polls.