Malawi's High Court has ordered the electoral board not to announce presidential results until ballots from a third of the voting districts have been recounted, after opposition complaints of rigging.
The main opposition Malawi Congress Party (MCP) of Lazarus Chakwera went to court after noticing what it claimed were irregularities in results from 10 of the country's 28 districts.
Opposition parties also complained that figures on many sheets were altered using correction fluid.
The court in the capital Lilongwe on Saturday ordered that "the announcement of presidential results is stayed until the results ... are verified through a transparent recounting of the ballot papers in the presence of representatives of political parties which contested the elections."
The electoral body, which has to announce the final results within eight days of voting, had on Friday suspended updating the tallies from the May 21 vote in order to resolve 147 complaints raised by some of the parties.
MCP spokesperson Eisenhower Mkaka said they turned to the courts because of "very glaring irregularities" noticed on results sheets turned in from polling stations.
Some of the documents showed "the same handwriting coming from different polling stations which are miles apart," he said, adding there was "a lot of tippexing".
"What we are seeing is a fraudulent election, the result has been tampered with."
He also said in some cases results were marked on improvised papers.
Another opposition presidential contender, Malawi's Vice President Saulos Chilima, has called for results to be annulled over "serious anomalies" reported during vote counting.
"These serious irregularities have, in fact, worsened and, in the process, the credibility and integrity of these elections have been significantly compromised," he told a news conference.
"In view of the chaos that has ensued ... I am calling upon the Electoral Commission for the nullification of the aggregated vote."
A count of votes tallied in three-quarters of the country's polling stations, released on Thursday, found incumbent President Peter Mutharika leading with 40.9 percent.
His closest challenger Chakwera of the MCP had 35.44 percent of the vote, while Vice President Chilima was on 18 percent.
Chakwera on Wednesday warned of alleged attempts to rig the vote, saying his MCP had conducted its own count and this, he maintained, showed he was ahead.
The European Union observer mission has described the vote as "well-managed, inclusive, transparent and competitive".
Malawi's 6.8 million voters also elected a new parliament and local government councillors in the 21 May vote.