The UN on Thursday called on Malawi authorities to free two organisers of protests against alleged election fraud who were arrested on suspicion of stealing money from AIDS programmes.

"UNAIDS respectfully requests the immediate release of the two members of the Mango Network, Mr Gift Trapence and Mr Macdonald Sembereka, from police custody," the UN programme to end AIDS said in a statement.

Mango is a network of non-profit groups in Malawi.

Trapence and Sembereka are members of the Human Rights Defenders Coalition that has organised countrywide protests since the disputed May 21 election, alleging the vote was tainted by fraud.

They were arrested on Tuesday for alleged misuse of UNAIDS funds.

Their arrest came just days after Mutharika claimed the protests were aimed at unseating his government and warned that the organisers would be dealt with.

According to a letter from the UN offices in Malawi, a UNAIDS staff member had on July 5 reported an alleged incident to the police.

"UNAIDS regrets unnecessarily involving the authorities in Malawi in its outstanding issue with the Mango Network," it said adding they "have amicably reached a resolution over the issue". 

"UNAIDS has not engaged in any legal action and believes there is no need for any legal action," it said in a statement.

Trapence has been at the forefront of the nationwide protests that have gripped the country since the re-election of President Peter Mutharika in May elections that opposition parties have dismissed as fraudulent.

Mutharika, who has been in power since 2014, was re-elected by 160,000 votes ahead of main challenger Lazarus Chakwera.

Over the weekend, dozens of people were arrested after Mutharika accused the protesters of plotting against his government.