"We need to have a stern warning for all of us: that this virus will rebound if we let it," Maria Van Kerkhove, the WHO technical lead for COVID-19, told a briefing.

"And we cannot let it."

WHO Director-General Tedros Adhanom Ghebreyesus said the rise was "disappointing but not surprising," noting that the upward trend was taking place everywhere apart from Africa and the western Pacific region.

It was too early for countries to rely solely on vaccination programs and abandon other measures, he said: "If countries rely solely on vaccines, they are making a mistake. Basic public health measures remain the foundation of the response."

Tedros noted that Ghana and Ivory Coast became the first countries on Monday to begin vaccinating people with doses supplied by COVAX, the international program to provide vaccines for poor and middle-income countries.

But he also criticised rich countries for hoarding vaccine doses, saying that it was in everyone's interest for vulnerable people to be protected around the world.

"It's regrettable that some countries continue to prioritise vaccinating younger healthier adults at lower risk of diseases in their own populations, ahead of health workers and older people elsewhere," Tedros said.

Mike Ryan, the WHO's top emergency expert, said the global fight against the coronavirus was in a better state now than it was 10 weeks ago before the roll-outs of vaccines had begun.

But it was too early to say the virus was coming under control.

"The issue is of us being in control of the virus and the virus being in control of us. And right now the virus is very much in control."

The Czech Republic, which is battling the world's worst surge in COVID-19 infections, deployed more police officers and soldiers on Monday to help enforce new lockdown measures that seek to confine people mostly to their home districts.

Prime Minister Andrej Babis has said the healthcare system faces collapse without the new restrictions due to a record number of patients in a serious condition.

The country of 10.7 million has recorded the highest per capita infection rate in the world over the last week, according to the Our World in Data website, 11 times higher than neighbouring Germany.

Exactly a year from when the first COVID-19 case was reported, authorities deployed around 26,000 police officers and 3,800 soldiers to enforce the three-week order limiting free movement, though there were exemptions for work-related travel.

The coronavirus-linked death toll in the country has doubled since mid-December to reach 20,469.

Meanwhile, French health authorities reported on Monday the number of people being treated in intensive care units for COVID-19 was up by 52, at 3544, going above the 3500 threshold for the first time since December 1.

Australian Associated Press