Zimbabwe's Movement for Democratic Change (MDC) has said it could take to the streets to challenge President Robert Mugabe's victory in an election it rejects as a farce.
No results of the presidential vote on 31 July have been announced.
However, Mr Mugabe's ZANU-PF has already claimed a resounding win and interim tallies of the parliamentary count suggest a massive victory for the 89-year-old, who has ruled since independence from Britain in 1980.
The African Union's monitoring mission chief has called Wednesday's peaceful polls generally "free and fair".
Western observers were kept out, but domestic monitors have described them as "seriously compromised" by registration flaws that may have disenfranchised up to one million people.
Observers from the Southern African Development Community, a regional grouping, described the elections as "free and peaceful" and called on MDC leader Morgan Tsvangirai to accept the result.
Mr Tsvangirai has already denounced the election as a "huge farce" marked by polling day irregularities and intimidation by ZANU-PF.
Western rejection of the regional African verdict on the election could stir tension, while acceptance of Mr Mugabe's victory will be slammed in countries where he is derided as a ruthless despot responsible for rights abuses and ruining the economy.
The mood on the streets of the capital Harare was subdued as the MDC's top leadership met at its headquarters to chart their next move, with everything from a legal challenge to street protests on the table.
"Demonstrations and mass action are options," party spokesman Douglas Mwonzora said.