The leading opposition presidential candidate in Republic of Congo is receiving oxygen in hospital after being diagnosed with Covid-19 on the eve of the country’s election.

Guy Brice Parfait Kolelas, 61, had missed his final campaign event on Friday after telling some reporters a day earlier that he feared he had malaria.

A relative said plans were under way for Mr Kolelas to be evacuated abroad for further treatment.

A video circulating on social media dated to Friday showed Mr Kolelas 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.”

A campaign spokesman confirmed the authenticity of the video and Mr Kolelas’ hospital admission. Two people at the hospital who had seen Mr Kolelas’s test results confirmed he had tested positive for coronavirus.

The impact of his illness on Sunday’s election is not clear. An article of the Congolese Constitution provides for a postponement if a candidate dies or is unable to participate in the vote.

There was no immediate reaction to the developments from the government or long-time President Denis Sassou N’Guesso.

Mr Kolelas finished second behind Sassou N’Guesso in the country’s 2016 presidential election with about 15% of the vote. The opposition figure has been particularly critical of the incumbent leader in recent days, declaring that Republic of Congo had become “a police state”.

Sassou N’Guesso is the third-longest serving president in Africa, ruling from 1979-1992 and then again since 1997 in the nation often overshadowed by its vast neighbour Congo.

Republic of Congo has had fewer than 10,000 confirmed cases of Covid-19 since the pandemic began, with 134 confirmed deaths.