A leading opposition figure called for "passive resistance" over the outcome of Wednesday's presidential and parliamentary elections, which the opposition and local monitors charge was riddled with flaws.
Mugabe's ZANU-PF forecast a landslide victory for the 89-year-old veteran leader over his longterm rival Prime Minister Morgan Tsvangirai, who is bidding to end his three-decade grip on power.
"It's the prediction that the president might likely get 70 to 75 per cent," party spokesman Rugare Gumbo told AFP.
But Tsvangirai, trying for the third time to unseat his firebrand rival, on yesterday slapped down the victory claims.
"It's a sham election that does not reflect the will of the people," he said, pointing to a litany of alleged irregularities.
"In our view this election is null and void," he said. "This election has been a huge farce."
Foreign diplomats and independent local election observers also expressed deep misgivings about the poll, the first since violent, flawed elections in 2008 which saw Mugabe and Tsvangirai forced into an uneasy power-sharing deal.
Tsvangirai, 61, stopped short of claiming victory himself, a move that could have enflamed tensions in the sanctions-hit country where political violence is common.
But top MDC official Roy Bennett called for a campaign of "passive resistance".
"I'm talking about people completely shutting the country down -- don't pay any bills, don't attend work, just bringthe country to a standstill."
"There needs to be resistance against this theft and the people of Zimbabwe need to speak out strongly.