The leading opposition presidential candidate in Republic of the Congo was receiving oxygen at a private hospital after learning he had Covid-19, a relative said. The diagnosis, on the eve of a national election, cast the poll on Sunday into doubt. Guy Brice Parfait Kolelas, 61, skipped his final campaign event on Friday after telling reporters a day earlier he feared he had malaria. Mr Kolelas is diabetic, placing him at raised risk of complications from Covid-19. A video circulating on social media dated Friday showed him wearing an oxygen mask and with a blood pressure cuff on his arm as he lay in a hospital bed. “My dear compatriots, I am in trouble. I am fighting death,” the candidate says in a weak-sounding voice after removing his oxygen mask. “However, I ask you to stand up and vote for change. I would not have fought for nothing.” Congo’s President Denis Sassou N’Guesso has been in power continuously for almost 24 years, last winning 60 per cent of the vote in 2016. But the Central African country’s constitution stipulates that an election can be delayed if a candidate dies or cannot take part in the vote. There was no immediate reaction to the developments from the government late on Saturday. Mr Kolelas placed second to Mr Sassou N’Guesso in the last presidential election with about 15 per cent cent of the vote. The opposition figure has been particularly critical of the incumbent leader in recent days, declaring that Congo had become “a police state”. Mr Sassou N’Guesso is the one of Africa’s longest-serving presidents, ruling from 1979-1992 and again since 1997. Republic of Congo has reported fewer than 10,000 cases of Covid-19 since the pandemic began, with 134 confirmed deaths. The country of 4,600,000, also known as Congo-Brazzaville, is often overshadowed by its vast neighbour Democratic Republic of the Congo.