Residents of parts of Shanghai and Beijing have been ordered to undergo further rounds of COVID-19 testing following the discovery of new cases in the two cities, while tight restrictions remain in place in Hong Kong, Macao and other Chinese cities.

Shanghai has only just emerged from a strict lockdown that confined most of its 24 million residents to their homes for weeks and the new requirements have stirred concerns of a return of such harsh measures.

The latest outbreak in China’s largest city, a key international business center, has been linked to a karaoke parlor that reopened without authorization during lockdown and failed to enforce prevention measures among employees and customers, including the tracing of others they came into contact with, according to the city health commission. All such outlets have been ordered to temporarily suspend business, the city’s department of culture and tourism said.

"The virus spreads quickly because such entertainment venues are mostly indoor and closed, with frequent movement of people, high concentrations of people and inadequate personal protection measures," said Zhao Dandan, deputy director of Shanghai’s municipal health commission.

Apartment blocks where cases are discovered continue to be isolated, while mass testing in the majority of the city’s 16 districts has been ordered at least through Thursday. A negative test result obtained within the previous 48 hours is required to enter residential compounds and public venues under the "two tests within three days" program.

Entertainment businesses from water parks to chess clubs and internet cafes have been wanting to reopen but face an uncertain regulatory environment.

Those types of venues will "gradually open in an orderly and strict manner according to the situation of epidemic prevention and control in each district," said Jin Lei, deputy director of the city’s culture and tourism department.