Everyone in Shenzhen will undergo three rounds of COVID-19 testing after 60 new cases were reported on Sunday.

All businesses except those providing essential goods such as food and fuel have been ordered to shut or operate from home.

The number of coronavirus cases in China's latest infection surge are low compared to 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.

As part of the clampdown, access to China's most populous city of Shanghai has been restricted with bus services suspended and a negative test required from anyone wanting to enter.

Shenzhen is home to some of China's most prominent companies, including telecoms equipment giant Huawei Technologies.

The authorities reported 1,938 new cases on the Chinese mainland on Sunday, more than triple the previous day's total.

Around three-quarters of those - 1,412 cases - were in Jilin province in the northeast, where entry to the industrial city of Changchun has been suspended and families were told to stay at home.

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 out of 115,466 confirmed cases since the pandemic started.

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, most of them elderly people, and 32,430 new cases.

This is down from above 50,000 after strict travel and business curbs were imposed.

Hong Kong, which has 7.4 million residents, is trying to contain an outbreak that has killed 3,993 people, most of them in the latest surge driven by the omicron variant, and swamped hospitals.

"People should not get the wrong impression that the virus situation is now under control," Dr Albert Au, an expert with the government's Centre for Health Protection, said.

"Once we let our guard down, it's possible that (infections) will bounce back and rise again."

On the mainland, 831 new cases were reported on Sunday in Changchun, 571 in the nearby provincial capital city of Jilin and 150 in the eastern port city of Qingdao.

Figures published earlier this week showed six million people have now died of coronavirus since the pandemic began.