HARARE, Zimbabwe — Longtime political rivals President Robert Mugabe and Prime Minister Morgan Tsvangirai said they each cast “yes” votes in a one-day referendum Saturday on a new constitution that curbs presidential powers and that is backed by all main political parties.
Mugabe said he voted yes to the home-grown constitution to show how Zimbabwe mapped out its own future without outside interference.
‘‘It gives us the right to determine together which way to govern ourselves,’’ he said.
Mugabe, 89, who led the nation to independence from Britain in 1980, has repeatedly accused Western governments of supporting efforts to oust him.
Tsvangirai, thronged by supporters while voting at a junior high school south of Harare, said a yes vote marked a new turning point ‘‘and one of the most important historical steps’’ for the southern African nation after years of political and economic turmoil. He said it paved the way for a new chapter of the rule of law.
His supporters who have been killed in political violence over the past decade ‘‘will rest in peace because this is the most important stage we have been fighting for,’’ Tsvangirai said. ‘‘I hope everyone will exercise their vote as a preliminary step to free and fair elections.’’
Full scale presidential and parliamentary elections are slated for July to end a shaky and dispute-ridden coalition government formed by regional leaders after the last violent and disputed national polls in 2008.
There were no immediate reports of violence Saturday after disturbances between rival youth groups on Friday.
Mugabe, voting at a school in western Harare, said on Saturday that he wanted peace to prevail.
‘‘Those who want to fight are allowed to if they are boxers or wrestlers, but to go about beating people in the streets, that’s not allowed,’’ he said.
Officials said polling was busy in populous districts after voting stations opened at 7 a.m. across the country. Small knots of voters turned out early in remote areas and less populated or wealthier suburbs.
The proposed constitution reduces the entrenched powers of Zimbabwe’s president and includes a range of democratic reforms demanded by regional mediators in Zimbabwe’s decadelong political and economic crisis.
The voting day was announced exactly a month ago, and critics say voters were not given enough time to study the constitutional proposals in detail. About 9,400 voting stations were set up and 12 million ballot papers have been printed. Results are expected within five days.
Since Tsvangirai, 61, the former opposition leader, founded his Movement for Democratic Change party four previous elections have been marred by violence and alleged vote-rigging blamed primarily on the ZANU-PF party of Mugabe.
The draft constitution reduces presidential powers to pass authoritarian decrees and paves the way for a National Peace and Reconciliation Commission on past violence and human rights violations.
It also strengthens the bill of rights to protect all Zimbabweans from ‘‘torture, cruel, inhumane and degrading treatment or punishment’’ that would be enforced by a new Constitutional Court with powers above the main existing highest court of appeal, the Supreme Court.