Zanu-PF said anomalies had been detected in a number of constituencies
President Robert Mugabe's party has asked Zimbabwe's electoral officials to delay presidential poll results to check "errors and miscalculations".
The opposition Movement for Democratic Change said the move was illegal - a recount is possible only after the result has been published.
They have asked the High Court to publish the outcome immediately.
The MDC believes its leader Morgan Tsvangirai won outright in the vote held eight days ago.
The opposition party has also denied it had proposed a unity government. A minister had earlier said Zanu-PF had rejected an opposition call for a coalition.
On Saturday, the opposition accused President Mugabe of "preparing a war".
And the farmers' union said a number of white-owned farms had been briefly invaded by war veterans' groups loyal to Mr Mugabe in southern Masvingo.
A spokesman said the situation was under control after police intervened to disperse them.
Mr Mugabe's Zanu-PF party has cited what it claims are anomalies in the presidential vote despite the fact the Zimbabwe Electoral Commission (ZEC) has still to release the result.
Information Minister Bright Matonga told the BBC the anomalies were with the collation of the results - there was a discrepancy between the voting results put outside polling stations and the form sent to the central election commission.
It was not clear if this meant the whole vote had to be counted again.
The minister insisted the request did not amount to a recount - which has been dismissed as illegal by MDC Secretary-General Tendai Biti.
"The [Electoral] Act says that you ask for a recount within 48 hours of the counting," he said.
"Counting takes place at polling stations so it's within 48 hours of that.
"It's madness literally and metaphorically".
According to papers submitted to the ZEC by Zanu-PF, the number of votes for Mr Mugabe recorded at a number of polling stations were reduced before being sent on to electoral officials.
Some ZEC officials working in the Midlands constituencies of Mberengwa East, West, North and South had since been arrested, the state-run Sunday Mail newspaper said.
"As will soon become apparent, the constituency elections officer and his team committed errors of miscounting that are so glaring as to prejudice not just our clients' candidate but also his co-contestants," Zanu-PF's letter said, according to the Sunday Mail.
In a separate article, the Sunday Mail quoted Justice Minister Patrick Chinamasa as saying the Zanu-PF had rejected an offer from Mr Tsvangirai to form a national unity government, but Mr Biti denied that an offer had been made.
Before the High Court judge on Sunday, MDC lawyer Alec Muchadehama said the results "must be announced forthwith", as they had been available since 30 March.
But ZEC lawyer George Chikumbirike said the court's remit did not include ruling on the case - only ZEC could adjudicate.
The court is to rule on Monday on whether it has jurisdiction over the case.
The Zanu-PF complaint came hours after the ZEC declared the final results of last week's Senate election. It said Mr Mugabe's party had won 30 seats, with the combined opposition taking the same number.
The MDC says Mr Tsvangirai took 50.3% of the presidential vote
In the lower house, opposition parties took 109 seats, while Zanu-PF won just 97 - the first time it has failed to win a majority since independence from the UK in 1980.
On Saturday Mr Tsvangirai claimed victory for the first time since the vote, saying figures posted outside polling stations confirmed he had reached the required threshold of more than 50% of the vote to win outright - making a run-off unnecessary.
He also claimed that the country's central bank was printing money "for the finance of violence", and called for dialogue on a peaceful transition.
Mr Mugabe, 84, came to power 28 years ago at independence on a wave of optimism.
But in recent years Zimbabwe has been plagued by the world's highest inflation, as well as acute food and fuel shortages, which correspondents say have driven many voters to back the opposition.