China reports most virus cases since pandemic start

China reported more than 20,000 Covid-19 cases on Wednesday, the highest daily tally given since the start of the pandemic, as millions in locked-down Shanghai began a new round of testing.

The country's "zero-Covid" strategy has come under immense strain as cases spike, with around 25 million residents of Shanghai -- China's largest city and economic engine room -- ordered to stay-at-home as the authorities struggle to contain the outbreak.

Until March, China had kept daily cases low with snap localised lockdowns, mass testing, and strict restrictions on international travel.

But the caseload has hit thousands per day in recent weeks, with Shanghai driving the surge of the highly transmissible Omicron variant.

The city locked down its residents in phases last week, prompting scenes of panic-buying and mass testing.

But state broadcaster CCTV reported that the city will launch a fresh round of tests on the entire population on Wednesday.

Shanghai is "testing its strength against the virus," senior city health official Wu Qianyu said at a press conference Wednesday, the latest dour warning from authorities suggesting a long run in lockdown may be ahead.

The city is converting its landmark National Exhibition and Convention Center into a makeshift Covid hospital for 40,000 people, state news agency Xinhua reported Wednesday, just days after setting up a temporary quarantine centre in another expo hall.

China recorded 20,472 infections on Wednesday, the National Health Commission said in a statement.

It is the country's highest-ever daily infection number given by authorities, even during the peak of the initial outbreak which centred around Wuhan.

The majority of the cases are, however,...