Malawi opposition supporters celebrated overnight after a landmark court ruling that declared incumbent President Peter Mutharika was "not duly elected" in a disputed 2019 vote.The country's constitutional court on Monday ordered a fresh vote within 150 days after it annulled the May election result over widespread irregularities, including the use of correction fluid on results sheets.It had been feared that the verdict would stoke turmoil in the normally peaceful southern African country.But there were scenes of jubilation overnight as opposition supporters chanted anti-Mutharika songs in the streets, sporadically setting off fireworks in the two largest cities of Blantyre and Lilongwe."It is a good time to be alive in Malawi. We have demonstrated that democracy does and can work in Africa. And this victory is not for us, it is for generations to come," said Lameck Hango, who celebrated with his friends in the capital Lilongwe.Another Lilongwe resident, Johnson Banda, said he was "very happy with this judgement". "It's a true indication that Malawi has true democracy and we really appreciate our court judgement."Read: Malawi's constitutional court cancels presidential vote resultThe Nation newspaper led with the headline "Null and void", while the Daily Times blared "It's fresh election".Businesses and shops re-opened on Tuesday after they pulled down their shutters the previous day fearing an outbreak of violence following the verdict.'The beauty with democracy' Mutharika, 79, will remain president until the new election because he was in power before the now-invalidated 2019 result. He has the right to appeal the verdict and has six weeks in which to do so.The main opposition Malawi Congress Party, which led the court challenge, hailed the ruling as "a very fair judgement" that had "set a precedent" for future elections.Mutharika supporter Chimpele Tsamwa was less pleased.VIDEO: ???? Supporters of the main opposition Malawi Congress Party (MCP) take to the streets of the capital Lilongwe to celebrate a court verdict nullifying the May 2019 presidential election result pic.twitter.com/nuORdLW0pR— AFP news agency (@AFP) February 4, 2020"The judgement is not what I expected nor wanted - but then all in all we trust the courts and have to go with what they have said. That's the beauty with democracy," he told AFP.In a historic ruling the five judges concurred that "the irregularities and anomalies have been so widespread, systematic and grave... that the integrity of the results has been seriously compromised".The court said only 23% of the results sheets had been able to be verified.The judges said that the results announced by Malawi's Electoral Commission "cannot be trusted as a true reflection of the will of the voters"."We hold that the first respondent (Mutharika) was not duly elected as president of Malawi on May 21, 2019," ruled lead judge Healey Potani.Neither the ruling party nor the presidency have commented on the verdict.But Mutharika has repeatedly dismissed opposition accusations that the poll was rigged and shrugged off doubts over the official results.'Respect the decision' Sporadic protests have broken out across the country since the election in May, when Mutharika was declared the winner by a narrow margin, with 38.5% of the vote.Runner-up Lazarus Chakwera, who lost by just 159 000 votes, said he was robbed of victory and took the matter to court.The case gripped the nation, keeping Malawians glued to their radios for hours on end as witnesses presented evidence of alleged vote-rigging during six months of hearings.It is the first time a presidential election has been challenged on legal grounds in Malawi since independence from Britain in 1964.The outcome echoes a historic decision by Kenya's judiciary to annul presidential election results over claims of widespread irregularities in 2017.International powers have sought calm."We call upon all Malawians to respect the decision of the court and to adhere to the path outlined in Malawi's constitution and electoral laws, including on the right to appeal," said Tibor Nagy, the top US diplomat for Africa.The European Union said in a statement that it "stands ready to accompany Malawi on the way ahead in view of preserving the unity and democratic credentials of the country".Zimbabwe's opposition MDC party also welcomed the ruling.