China reported over 20,000 Covid-19 cases on Wednesday, the highest daily tally given since the start of the pandemic, with Shanghai the heart of the virus surge despite being in lockdown.
The country's "zero-Covid" strategy has come under immense strain as cases spike.
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 officials saying they have detected a mutation of the highly transmissible Omicron variant near Shanghai.
China recorded 20,472 infections on Wednesday, the National Health Commission said in a statement, adding that there were "no new deaths."
It is the country's highest-ever daily infection number given by authorities, even during the peak of the initial outbreak which centreed around Wuhan.
The majority of the cases are, however, asymptomatic.
The COVID-19 outbreak in China’s largest metropolis of Shanghai remains “extremely grim” amid an ongoing lockdown confining around 26 million people to their homes, a city official said Tuesday.
The director of Shanghai’s working group on epidemic control, Gu Honghui, was quoted by state media as saying that the outbreak in the city was “still running at a high level.”
“The situation is extremely grim,” Gu said.
China has sent more than 10,000 health workers from around the country to aid the city, including 2,000 from the military, and is mass testing residents, some of whom have been locked down for weeks.
Most of eastern Shanghai, which was supposed to reopen last Friday, remained locked down along with the western half of the city.
Shanghai recorded another 13,354 cases on Monday — the vast majority of them asymptomatic — bringing the city’s total to more than 73,000 since the latest wave of infections began last month. No deaths have been ascribed to the outbreak driven by the omicron BA.2 variant, which is much more infectious but also less lethal than the previous delta strain.
Chinese authorities have extended their lockdown of Shanghai to cover all its 25 million people after a fresh surge in Covid cases.
Initially, there had been separate measures for the eastern and western sides, but the whole city is now subject to indefinite restrictions.
Shanghai is the largest single city to be locked down to date.
The important financial hub has battled a new wave of coronavirus infections for more than a month.
The city is testing the limits of China's zero-Covid strategy, amid growing public anger over quarantine rules.
The policy sets China apart from most other countries which are trying to live with the virus.
But the increased transmissibility and milder nature of the Omicron variant has led to questions over whether the current strategy is sustainable in the long run.
