The southern business centre of Shenzhen, a city of 17 million people, has been shut down by the government due to a rise in coronaviruses.
Shenzhen, a finance and technology centre that abuts Hong Kong, will undergo three rounds of testing after 60 new cases were reported on Sunday. The businesses that supply food, fuel and other necessities were ordered to close or work from home.
The number of cases in China is low compared with other countries and with Hong Kong, which reported more than 30,000 on Sunday. The mainland government has reported more than one thousand new cases. That is more than Saturday's total. The authorities on the mainland have a zero tolerance policy and have locked down the entire cities to find and find out who has the disease.
In Jilin province in the north-eastern part of the country, about three-quarters of the cases were, and the city of Changchun was placed under a curfew on Friday due to a number of infections.
Shenzhen is home to some of China's most prominent companies, including telecom equipment maker Huawei Technologies, electric car brand BYD Auto, and Ping An Insurance Co.
Out of 115,466 confirmed cases of the coronaviruses, China has reported a total of 4,636 deaths.
The number of cases in the most populous city in China rose by 15.
The city health agency said those who come or return to the city must have a negative nucleic acid test report within 48 hours.
In Hong Kong, a health official warned the public not to assume the territory's deadly coronavirus surge was under control as the government reported 190 new deaths and 32,430 new cases. After stringent travel and business curbs were imposed, that is down from over 50,000.
Hong Kong, a crowded financial hub of 7.4 million, is trying to contain an outbreak that has killed 3,993 people, most of them in the latest surge driven by the Omicron variant.
Dr Albert Au, an expert with the government's Center for Health Protection, said that people should not get the wrong impression that the situation is under control.
Construction crews from the mainland built temporary isolation centers in Hong Kong for thousands of patients.
In Changchun, Jilin City, and the eastern port city of Qingdao there were new cases.
Jilin authorities are stepping up their anti-disease measures after concluding that their earlier response was inadequate, according to the deputy director of the provincial Health Commission.
The emergency response mechanism in some areas is not sound.
Cangzhou residents were told to stay home after nine cases were reported there, according to a government notice.