Malawi's opposition leader Lazarus Chakwera was sworn in Sunday as the southern African country's new president after winning the re-run of a hotly disputed election.

It was a dramatic reversal of fortune for the incumbent Peter Mutharika, whose victory in a May 2019 ballot was overturned by the Constitutional Court over fraud allegations.

Chakwera, a former evangelist preacher, was declared the winner of the election replay held on Tuesday with almost 59 percent of the vote, according to results announced late Saturday.

Malawi is only the second African country south of the Sahara to have presidential poll results overturned in court, after Kenya in 2017.

And it is the first time in the region that a vote re-run has led to the defeat of an incumbent leader.

"I do solemnly swear that I will well and truly perform the functions of the high office of the president of the Republic of Malawi and that I will preserve and defend the constitution," the 65-year-old Chakwera said as took his oath before thousands of supporters.

Opposition candidate Saulos Chilima was sworn in as vice-president.

Some 6.8 million Malawians returned to the polls on Tuesday after the country's top court found the first election had been marred by widespread irregularities -- including the use of correction fluid to tamper with result sheets.

Chakwera was pronounced the winner with 2.6 million votes, while Mutharika took 1.75 million and underdog candidate Peter Dominico Kuwani over 32,400.

Voter turnout was just under 65 percent.

In power since 2014, Mutharika had won 38 percent of the discredited vote last year, just ahead of Chakwera with about 35 percent.