Zimbabwe President Robert Mugabe's ZANU-PF has secured a two-thirds parliamentary majority, allowing it to change the constitution at will.
The opposition rejected the result and joined Western governments in denouncing the vote as a fraud, saying Mr Mugabe had stolen his third election in five years.
"We have rejected the results because we don't believe they reflect the will of the people," said Morgan Tsvangirai, who leads the Movement for Democratic Change (MDC).
Police warned the opposition they would crush any violent reaction to Mugabe's victory. With all but five of 120 constituencies reporting, Mugabe's ZANU-PF party won 74 seats against 40 for the MDC.
One independent, purged former Information Minister Jonathan Moyo, was also elected.
Mr Mugabe, who has ruled for 25 years, by law will appoint 30 additional members of the 150-seat legislature, boosting ZANU-PF's majority.
The MDC, once seen as the most potent challenge to Mr Mugabe since independence from Britain in 1980, was expected to post a net loss of as many as 10 seats.
Mr Tsvangirai has said the election was marked by fraud, fear and intimidation - an assessment echoed by the United States, Britain and other Western nations. US Secretary of State Condoleezza Rice accused Mr Mugabe of policies "designed to repress, crush and otherwise stifle expressions of differences in Zimbabwe."
Mr Tsvangirai, who has accused Mr Mugabe (81), of rigging previous elections in 2000 and 2002, hinted yesterday his supporters may take their anger to the streets rather than attempt to fight the result in court. Today, the opposition leader said strategy was still being discussed.
Police vowed to crush any post-poll violence and were setting up check-points on highways and patrolling streets in the towns and cities.
Mr Mugabe has dismissed criticism of the election, which he said was as free and fair as any in the world.
Analysts say the party could use its majority to push through constitutional changes to protect Mr Mugabe from the kind of prosecutions that have plagued some other African leaders when they stepped down. Mr Mugabe is due to retire in 2008.
Critics accuse him of ruining once-prosperous Zimbabwe by a chaotic seizure of white farms for landless blacks and economic mismanagement which has brought huge inflation, unemployment and food and fuel shortages.
The President blames his Western critics for sabotaging the economy and had demanded an overwhelming ZANU-PF victory to see off the challenge from the MDC, which he pillories as a British puppet.