BEIJING - More than 5,000 people are probably dying each day from COVID-19 in China, health data firm Airfinity estimated, offering a dramatic contrast to official data from Beijing on the country's current outbreak.

The UK-based firm said it had used modelling based on regional Chinese data to produce figures that also put current daily infections in the country at above a million.

Its estimates were "in stark contrast to the official data which is reporting 1,800 cases and only seven official deaths over the past week," it said in a statement.

China's National Health Commission (NHC) did not immediately respond to a request from Reuters for comment. On Thursday it reported no new COVID-19 deaths and 2,966 new local symptomatic cases for Dec. 21.

A senior World Health Organization official said on Wednesday that China might be struggling to keep a tally of COVID infections as it experiences a big spike in cases.

An abrupt U-turn by China on its previous zero-COVID policy following protests has raised global concerns of widespread infections among a vulnerable, undervaccinated population. It has stopped mass testing and no longer reports asymptomatic cases.

Airfinity said its mortality risk analysis suggested between 1.3 to 2.1 million people could die in China's current COVID outbreak. Analyses by other modelling groups have also predicted as many as 2.1 million deaths.

Airfinity estimates the wave could have two peaks at 3.7 million a day in mid-January in regions where cases are currently rising and 4.2 million a day in March in other provinces.

Cases were currently rising fastest in Beijing and the southern province of Guangdong, said the firm.

According to its website, in 2020 it built "the world's first dedicated COVID-19 health analytics and intelligence platform which is now the trusted source of decision makers and media globally."

This week, a leading Chinese medical expert said only deaths caused by pneumonia and respiratory failure after contracting COVID will be classified as having been caused by the coronavirus.

Airfinity's Head of Vaccines and Epidemiology Dr Louise Blair said this change was "different to other countries that record deaths within a time frame of a positive test (and)... could downplay the extent of deaths seen in China."

(Reporting by Martin Quin Pollard; Writing by Liz Lee; editing by John Stonestreet)