The ruling party is challenging the count in 23 parliamentary races, most won by the opposition, including in President Robert Mugabe's home district of Zvimba. The counting began after an opposition attempt to stop it was blocked in court Friday. The court is stacked with Mugabe loyalists.
The opposition has also gone to court to try to force the release of results from the presidential vote. Three weeks after the March 29 elections, which Mugabe is widely believed to have lost, they have not yet been published.
Results from legislative races held alongside the presidential votes gave control of the parliament to the opposition for the first time.
In Zvimba, officials excluded reporters as the count began in the presence of officials from the ruling and opposition parties as well as local observers.
Reporters saw no international observers present, though the state-controlled Herald newspaper quoted officials of the Southern African Development Community as saying it had sent 50 monitors.
In one contested constituency, The Herald reported a failed petrol bomb attack on offices where ballot boxes were stored early Friday morning. The newspaper quoted police as saying three attackers threw a homemade bomb at the Gutu district administration office, but that it did not explode. It said the attackers drove away when challenged by a police officer.
The state-owned Zimbabwe Broadcasting Corp. reported the re-count would take as many as three days.
Opposition leader Morgan Tsvangirai claims he won the election outright and has accused Mugabe of planning to hold onto power simply by refusing to release the election results
The opposition Movement for Democratic Change has said that the delays have provided the ruling party a chance to brutalize and intimidate voters to suppress political dissent while it attempts to engineer a runoff vote.
The independent Zimbabwe Doctors for Human Rights says at least 200 people have been treated for severe injuries since the election. The group was investigating at least two reported but unconfirmed deaths.
New York-based Human Rights Watch charged in a report released Saturday that "torture and violence are surging in Zimbabwe."