President Mugabe has ignored opposition calls to stand down
A Zimbabwean High Court judge has ruled that he can hear a petition by the opposition demanding the immediate release of the recent election results.
He dismissed the Zimbabwe Electoral Commission's (ZEC) argument that his court did not have jurisdiction and set the case for Tuesday.
Opposition leader Morgan Tsvangirai has said he defeated President Robert Mugabe in the presidential election.
No results have yet emerged from the 29 March presidential race.
Although the judge said he did have jurisdiction in the matter, he said he would decide on Tuesday whether to treat it as an urgent case, before hearing the actual arguments.
"I think ZEC just wants to delay this whole thing," said opposition Movement for Democratic Change (MDC) lawyer Alec Muchadehama.
The ZEC lawyer said the votes were still being verified, while the ruling party's demands for a recount was also delaying matters.
Meanwhile, two foreign nationals accused of working as journalists without accreditation have been freed on bail.
New York Times correspondent Barry Bearak and a British national were released on bail of 300m Zimbabwe dollars (US$10,000 at the official exchange rate, US$6 on the black market).
They were ordered to surrender their passports and appear in court on Thursday.
Earlier, Mr Mugabe called on the black population to ensure white farmers did not regain seized land, reports say.
He said black Zimbabweans could not afford to "retreat in the battle for land", the Herald newspaper said.
At least 18 of Zimbabwe's few remaining white-owned farms have been invaded since Saturday, farmers say, raising fears of renewed violence ahead of a possible run-off in the presidential election.
While Mr Tsvangirai's MDC says he won outright, an independent monitoring group says he came first with 49% of the vote - meaning a run-off would be needed.
Mr Tsvangirai says Mr Mugabe is "preparing a war on the people".
The MDC leader is currently in South Africa. His spokesman said Mr Tsvangirai would be holding private meetings.
In an article published on Monday, the state-run Herald newspaper quoted Mr Mugabe as saying Zimbabwe's black population had to protect their land from white farmers.
"Land must remain in our hands. The land is ours, it must not be allowed to slip back into the hands of whites," he is quoted as saying.
In 2000, there were 4,000 white farmers working on much of the best land in Zimbabwe.
Just 300 now remain after a campaign of often violent land seizures, with the land redistributed to black farmers.
Mr Mugabe says land is the most important issue in Zimbabwe and accuses the opposition of planning to return land to white farmers - this is denied by the MDC.
War veterans were blamed for violence in Zimbabwe's previous elections
Trevor Gifford, president of the Commercial Farmers Union, said some 23 farms had been occupied in the southern Masvingo province and around Centenary in the north-east.
"The police have intervened twice in Masvingo but they can't do much about it since it's state-sponsored and orchestrated from the highest office of the land," he told the AFP news agency.
On Friday, war veterans' leader Jabulani Sibanda accused white farmers of reoccupying farms allocated to blacks, and of telling other black farmers to leave or else face the wrath of an "incoming MDC government".
"We will defend our sovereignty. We will be compelled to repel that invasion," Mr Sibanda told reporters.
The war veterans association was instrumental in the invasion of white-owned farms ahead of parliamentary elections in 2000.
This turned many rural parts of the country into no-go areas for the opposition.
This year's election has been relatively peaceful and the opposition was able to campaign across the country.
The Zanu-PF has asked the ZEC for a further delay in declaring the results because of what it called "errors and miscalculations" in their compilation.
But the MDC has said the ruling party wants the delay to help Mr Mugabe find a way to cling to power.
The MDC says Mr Tsvangirai took more than 50% of the presidential vote
"It's ridiculous and absurd to talk of a recount before you know what the result is," Mr Tsvangirai said on Sunday.
The ZEC has declared the final results of the Senate election, which took place on the same day as the presidential poll. It said Zanu-PF had won 30 seats, with the combined opposition taking the same number.
In the lower house, opposition parties took 109 seats, while the Zanu-PF won just 97 - the first time it has failed to win a majority since independence.
Mr Mugabe came to power 28 years ago 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.