The leading opposition presidential candidate in Congo-Brazzaville has died hours after polls closed after becoming seriously ill with Covid-19.

Guy-Brice Parfait Kolelas died in a medical plane as he was being evacuated to France, his campaign director said.

Hours earlier the 61-year-old had appeared in a video shared on social media, where he removed his oxygen mask and told his supporters that he was "fighting death".

He urged them to vote in Sunday's poll.

The electoral law doesn't annul the election if one of the candidates dies.

Mr Kolelas, who was diabetic, was one of six candidates running against President Denis Sassou Nguesso, 77, who has been in power since 1979, except for a five-year period after losing elections in 1992.

Congo-Brazzavile has officially recorded more than 9,000 cases of Covid-19 and 130 deaths.

Mr Kolelas had missed his final campaign event on Friday after saying a day earlier that he feared he had malaria, the Associated Press news agency reports.

He was admitted to a private hospital in the capital, Brazzaville, and it was later confirmed that he had Covid-19.

Speaking in French from his hospital bed, Mr Kolelas said: "My dear compatriots, I am in trouble. I am fighting death. However, I ask you to stand up and vote for change. I would not have fought for nothing."

The head of the government's Covid-19 response team, Elira Dokekias, said that Mr Kolelas' condition had been serious on Saturday, the Associated Press reports.

After casting his ballot in the capital, Mr Sassou Nguesso had wished Mr Kolelas a swift recovery.

A large crowd gathered to catch a glimpse of the president, with many people not wearing masks and failing to adhere to social distancing rules.

Mr Sasou Nguessou beat Mr Kolelas in the last election in 2016, obtaining 60% of the vote compared with his rival's 15%.

The watchdog group NetBlocks reported that the internet had been shut down ahead of Sunday's voting.

The largest opposition party, the Pan-African Union for Social Democracy (UPADS), is boycotting the election, saying it fears the poll could divide the nation.

Congo-Brazzaville's Catholic Church episcopal conference has said it has "serious reservations" about the election's transparency.

A foregone conclusion

Analysis by Will Ross, BBC World Service Africa editor

It is hard to find anyone who thinks President Sassou Nguesso could lose this election.

After the last poll, two of his rivals were locked up. Some opposition parties argue the entire electoral system is run by the ruling party.

Suspicions of foul play will not have been helped when the internet was cut off.

Critics of the president say new leadership is needed in a country where more than half of the population is under-25. The economy, too, has been hit hard by a fall in the price of crude oil and the effects of the coronavirus pandemic.