The number of new infection cases with the novel coronavirus in China hit a record high, exceeding 20,000, the health authorities said Wednesday, casting doubt on the effectiveness of the country's radical "zero COVID" policy.

Across the mainland, 20,472 people, including asymptomatic ones, were confirmed to be infected with the virus on Tuesday, the highest in two years, according to the Chinese government.

A man takes a PCR test for the novel coronavirus in Shanghai on April 4, 2022. (Kyodo)

In China's financial and commercial hub of Shanghai, many parts of which have still been locked down since late March, the number of new infections reached 17,077 the same day, as the highly contagious Omicron variant spreads.

The Shanghai municipal government said at a press conference Wednesday it will carry out nucleic acid testing on all residents again to consider when it will lift the current lockdown.

The Global Times, a tabloid of the ruling Communist Party, quoted the National Health Commission as saying China should unwaveringly stick to the dynamic zero-COVID policy as infection cases "spike."

With infections expanding, Changchun, the capital of the northeastern province of Jilin, has also been sealed for more than a month.

The leadership of President Xi Jinping has maintained strict COVID-19 restrictions, such as imposing lockdowns on cities when outbreaks occur and quarantine on travelers from abroad, even following the end of the Beijing Winter Olympics and Paralympics.

Many Chinese citizens are believed to be frustrated by all-encompassing constraints under the Communist Party's policy, now in place for more than two years.

A Chinese man in his 30s, living in Shanghai, urged the central government to "change its policy," which is likely to be ineffective against the Omicron variant, saying he has been struggling to obtain adequate daily necessities amid the lockdown.