HARARE, Zimbabwe -- Zimbabwe's main opposition party on Friday filed a legal challenge to the results of the country's first election without Robert Mugabe on the ballot, alleging irregularities and calling for a fresh vote or for their candidate Nelson Chamisa to be declared the winner.

The filing brings more uncertainty to a country that had hoped the peaceful vote would begin a new era but has been rocked by scenes of military in the streets and opposition supporters harassed and beaten.

The court now has 14 days to rule, and Justice Minister Ziyambi Ziyambi said the inauguration, once planned for Sunday, "is on hold' until then.

Lawyers for the Movement for Democratic Change party arrived at court less than an hour before the deadline to submit papers. "We have a good case and cause!" Chamisa said on Twitter.

The Zimbabwe Electoral Commission has said President Emmerson Mnangagwa and the ruling ZANU-PF party won the July 30 election, with the president receiving 50.8 per cent of the vote and Chamisa receiving 44.3 per cent.

"We have managed to place before the courts all the mathematical and statistical irregularities," lawyer Thabani Mpofu told journalists as they emerged from the courthouse. A copy of the filing was not immediately available.

The opposition has claimed since shortly after the election that the vote was rigged but withheld evidence for the court challenge. A number of grassroots groups and NGOs that fanned out across the country have released reports questioning high turnout in some areas, striking differences in the number of voters for president and parliamentary seats in some cases and other concerns.

Mnangagwa, an ex-vice-president and Mugabe's longtime confidant and enforcer, says he wants to make Zimbabwe more open and democratic. Mugabe resigned in November after a military takeover, and many Zimbabweans were euphoric at his departure after decades of economic and political paralysis.

Two days after the election, however, soldiers opened fire during opposition protests in the capital, Harare, with six people killed. Foreign governments, Western election observers and human rights activists have expressed concern about the "excessive" force and the reports of opposition supporters being targeted by security forces since then.

On Thursday, senior opposition figure Tendai Biti was charged with inciting public violence and declaring unofficial election results as fears grew about a government crackdown. Biti asserted before the electoral commission's official announcement that Chamisa was the real winner.

Biti first fled to Zambia, where authorities denied asylum and handed him over to Zimbabwean security forces in defiance of a Zambian court order. The United States and several other nations, as well as the U.N. refugee agency, have expressed grave concern.

In a court appearance on Friday, Biti said he had fled Zimbabwe because he felt his life was in danger.

Mnangagwa's claim that Biti was freed because of his intervention is "a point of huge concern" at a time when the opposition is challenging the election results in court, Dewa Mavhinga, southern Africa director for Human Rights Watch, said in a live appearance on Facebook.

"It does raise serious questions about the independence of the judiciary in Zimbabwe," he said.

Some opposition leaders have expressed skepticism that the courts would fairly assess the election challenge, saying they are biased toward the government. Mpofu disagreed.

"We wouldn't have come to court if we thought that the court would not give us a fair hearing," he said.

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Associated Press writer Christopher Torchia in Johannesburg contributed.