Everyone in Shenzhen, a finance and technology centre that abuts Hong Kong, will undergo three rounds of testing after 60 new cases were reported Sunday.

All businesses except those that supply food, fuel and other necessities were ordered to close or work from home.

Case numbers in China's latest infection surge are low compared with other countries and with Hong Kong, which reported more than 32,000 on Sunday.

But mainland authorities are enforcing a "zero tolerance" strategy and have locked down entire cities to find and isolate every infected person.

Shenzhen is home to some of China's most prominent companies, including telecom equipment maker Huawei Technologies Ltd., electric car brand BYD Auto, Ping An Insurance Co. and Tencent Holding, operator of the popular WeChat message service.

On the mainland, the government reported 1,938 new cases, more than triple Saturday's total.

About three-quarters, or 1,412 cases, were in Jilin province in the northeast, where access to the industrial metropolis of Changchun was suspended on Friday and families were told to stay home after a spate of infections.

The territory's leader, Chief Executive Carrie Lam, warned on Saturday the peak of the latest infection surge might not be past yet.

China, where the first coronavirus cases were detected in late 2019 in the central city of Wuhan, has reported a total of 4,636 deaths on the mainland since the pandemic started out of 115,466 confirmed cases.

On Sunday, 831 new cases were reported in Changchun, 571 in the nearby provincial capital city of Jilin, 150 in the eastern port city of Qingdao and 60 in Shenzhen, a business centre adjacent to Hong Kong.

Authorities in Jilin are stepping up anti-disease measures after concluding their earlier response was inadequate, according to Zhang Yan, deputy director of the provincial Health Commission.

"The emergency response mechanism in some areas is not sound enough," Zhang said at a news conference, according to a transcript released by the government.

In Shanghai, China's most populous city with 24 million people, the number of cases in the latest surge rose by 15 to 432.

The city government called on the public not to leave unless necessary.

It said inter-city bus service would be suspended starting on Sunday.

"Those who come or return to Shanghai must have a negative nucleic acid test report within 48 hours before arrival," said a city health agency statement.

Also Sunday, some residents of Cangzhou, south of Beijing, were told to stay at home after nine cases were reported, according to a government notice.

It wasn't clear how many of its 7.3 million people were affected.

"Please do not leave Beijing unless necessary," a spokesman for the capital's Communist Party committee, Xu Hejian, was cited as saying by state TV.