China is expanding lockdowns, including in a cental city where factory workers clashed this week with police, as its number of COVID-19 cases hit a daily record.
People in eight districts of Zhengzhou with a total of 6.6 million residents were told to stay home for five days beginning on Thursday, except to buy food or get medical treatment.
Daily mass testing was ordered in what the city government called a "war of annihilation" against the virus.
During clashes on Tuesday and Wednesday, Zhengzhou police beat workers protesting over a pay dispute at the biggest factory for Apple's iPhone.
China's new cases reported in the past 24 hours was 31,444, the National Health Commission said on Thursday.
That is the highest daily figure since the coronavirus was first detected in the city of Wuhan in late 2019.
The daily average of reported cases is steadily increasing. This week, authorities reported China's first COVID-19 deaths in six months, bringing the total to 5232.
While the numbers of cases and deaths are relatively low compared with countries, China's ruling Communist Party remains committed to its "zero-COVID" strategy, which aims to eliminate the virus entirely.
Businesses and communities from the manufacturing centre of Guangzhou in the south to Beijing in the north have also been placed under various forms of lockdown.
Guangzhou suspended access on Monday to its Baiyun district of 3.7 million residents, while residents in parts of Shijiazhuang, a city of 11 million people, were told to stay home while mass testing was conducted.
Beijing opened a hospital in an exhibition centre. Some shopping centres and office buildings were closed and access was blocked to some apartment compounds.
The party is trying to contain the latest wave without shutting down its economy as it did in early 2020.
Its tactics include "closed-loop management," under which workers live in their factories with no outside contact.
Foxconn, the world's biggest contract assembler of smartphones, is struggling to fill orders for the iPhone 14 after thousands of employees walked away from the factory in Zhengzhou last month following complaints about unsafe working conditions.
Foxconn, based in Taiwan, said its contractual obligation about payments "has always been fulfilled".
The company denied reports that employees with the virus lived in dormitories at the factory.
It said facilities were disinfected and passed government checks before employees moved in.