Zimbabwe’s government has warned candidates could be jailed for prematurely announcing election results after Nelson Chamisa’s opposition MDC Alliance claimed to have won the general election and suggested it would call supporters on to the streets if the official result favoured Emmerson Mnangagwa, the president.

Mr Chamisa, a 40-year-old lawyer and preacher, said he was “winning resoundingly” as counting got under way and called on the country’s electoral commission to “perform their constitutional duty to officially announce the people’s election results”.

But Zimbabwe’s electoral authorities had announced the results from just seven parliamentary constituencies by Tuesday evening, and made no comment on the outcome of the presidential race.

Zimbabwean law forbids anyone other than the electoral commission from announcing results.

“As a government we have noted with concern the actions and conduct of some political party leaders... who are openly declaring that they will announce results irrespective of provisions of the law,” said Obert Mpofu, the home affairs minister, at a media briefing in Harare.