Half a million people in a single Chinese city are being infected with Covid-19 every day, a senior health official has said, in a rare and quickly censored acknowledgment that the country's wave of infections is not being reflected in official statistics.

China this month has rapidly dismantled key pillars of its zero-Covid strategy, doing away with snap lockdowns, lengthy quarantines, and travel curbs in a jarring reversal of its hallmark containment strategy.

Cities across the country have struggled to cope as surging infections have emptied pharmacy shelves, filled hospital wards, and appeared to cause backlogs at crematoriums and funeral homes.

But the end of strict testing mandates has made caseloads virtually impossible to track, while authorities have narrowed the medical definition of a Covid death in a move experts have said will suppress the number of fatalities attributable to the virus.

A news outlet operated by the ruling Communist Party in Qingdao on Friday reported the municipal health chief as saying that the eastern city was seeing "between 490,000 and 530,000" new Covid cases a day.

The coastal city of around 10 million people was "in a period of rapid transmission ahead of an approaching peak", Bo Tao reportedly said, adding that the infection rate would accelerate by another 10 percent over the weekend.

The report was shared by several other news outlets but appeared to have been edited by Saturday morning to remove the case figures.

China's National Health Commission said Saturday that 4,103 new domestic infections were recorded nationwide the previous day, with no new deaths.

In Shandong, the province where Qingdao is located, authorities officially logged just 31 new domestic cases.

China's government keeps a tight leash on the country's media, with legions of online censors on hand to scrub out content deemed politically sensitive.

Most government-run publications have downplayed the severity of the country's exit wave, instead depicting the policy reversal as logical and controlled.

But some outlets have hinted at shortages of medicine and hospitals under strain, though estimates of actual case numbers remain rare.

The government of eastern Jiangxi province said in a Friday social media post that 80 percent of its population — equivalent to around 36 million people — would be infected by March.

More than 18,000 Covid patients had been admitted to major medical institutions in the province in the two weeks up to Thursday, including nearly 500 severe cases but no deaths, the statement said.