Malawi (BBN)-Malawi's President Joyce Banda says she is annulling this week's general election - in which she was a candidate - because of voting "irregularities".
Banda had earlier said the vote had been marred by rigging, multiple voting and computer-hacking.
She said a new vote should be held within 90 days but she would not stand again in any new poll.
However, correspondents say it is unclear whether the Malawian president has the power to order an election.
Late on Friday, the Malawi Electoral Commission (MEC) said rival candidate Peter Mutharika had taken a lead of 42 percent, with 30 percent of votes counted.
Joyce Banda was in second place with 23 percent, the commission said.
Banda had previously accused a party, which she did not name, of infiltrating and hacking the MEC's counting system.
The MEC's chairman denied that its system had been hacked.
Around 7.5 million people were eligible to vote in the fifth elections since the end of one-party rule 20 years ago.
This was the first time that Malawi held presidential, parliamentary and local elections on the same day.
BBN/AD-24May14-5:30pm (BST)