Confirmed deaths from COVID-19 in Colombia passed 80,000 on Friday with intensive care units almost full in the biggest cities, where large crowds have been gathering for weeks of anti-government protests.

Authorities warned this week that the demonstrations - initially called in opposition to a now-canceled tax reform but which have expanded to tackle inequality and police brutality - were set to prolong an already-devastating third wave of the epidemic.

Bogota's mayor echoed that warning, saying the capital had on Thursday reported its second-highest number of new COVID-19 cases and highest number of deaths since the pandemic began.

"I don't know what more to say, to warn, to beg, to plead," Claudia Lopez said in a Twitter message late on Thursday that urged people to stick to social-distancing rules.

On Friday she announced she was infected and would self-isolate.

Demonstrators have marched across Colombia since April 28, around the time that nationwide daily deaths hit a record 505. Average deaths are hovering around 470 per day and on Friday the cumulative toll reached 80,250

The pressure on ICUs in the capital "is worrying," the government said late on Thursday, adding patients would be transferred by air to other cities.

ICU occupancy for COVID-19 patients in Bogota stands at 94%, according to local authorities. In Medellin and Cali, the rates are at 99% and 95%, respectively.

Health experts say they respect people's right to protest, but warn large groups cannot continue to gather.

"We can't go on like this," Andrea Ramirez, an epidemiologist at Bogota's Universidad de los Andes, told Reuters.

"We're now talking about an almost life-or-death situation, as right now if people get sick and need an ICU, they won't find one."