Malawi's new president Lazarus Chakwera was sworn in for a five-year term on Sunday, hours after unseating former leader Peter Mutharika in a re-run election.

Chakwera, 65, won 58.57% of the vote in Tuesday's poll, a dramatic reversal of the result of the original election in May 2019, which was later overturned by the courts.

The repeat vote was regarded by analysts as a test of the ability of African courts to tackle ballot fraud and restrain presidential power.

"To stand before you as president today is an honour. It's an honour that fills with unspeakable joy and immense gratitude," Chakwera said in his acceptance speech.

"With your help, we will restore a new generation's faith in the possibility of having a government that serves, not a government that rules," he told a cheering crowd dressed in the colours of his own Malawi Congress Party (MCP) and the allied party of Vice President Saulos Chilima.

MCP is Malawi's founding party and Chakwera's win brings it back into power after 26 years in opposition.

The judiciary infuriated Mutharika in February by overturning the result of the May 2019 election that had given him a second term, citing irregularities, and ordering a re-run. Mutharika's disputed win had sparked months of anti-government demonstrations, a rare sight in Malawi.

Mutharika said on Saturday there had been voting irregularities including violence and intimidation against his party's election monitors, but his complaint was dismissed by the electoral commission.

Critics had accused Mutharika of doing little to tackle corruption.

"Curbing corruption is crucial now more than ever," said Lauryn Nyasulu, president of the Economics Association of Malawi.

"The government needs to seal all loopholes and use whatever resources available in efforts to rebuild the economy and safeguard the welfare of those that have been heavily affected by the Covid-19 pandemic."