Shanghai has since Sunday enhanced supervision of the service sector to enforce all COVID-19 epidemic prevention and control measures and prevent a rebound of a local wave, an official said at a press briefing on Monday.

The campaign focuses on supermarkets, wholesale markets, restaurants, barber shops and hotels and their process of entrance management, staff management, venue disinfection and personal protection measures, said Shen Weizhong, deputy head of the supervision and guidance group under the Shanghai COVID-19 epidemic prevention and control leadership group.

"So far, we've found some service venues didn't implement epidemic prevention and control protocols strictly. Some didn't limit capacity, and others didn't require social distancing in waiting areas," Shen said. "Also, some didn't mandate customers to scan the venue health code, and some employees didn't undergo nucleic acid tests daily as required."

Shen said the loopholes will be rectified or the enterprises will be made public and face legal punishment.

Officials from the Shanghai Health Commission said on Sunday service venues were a main source of COVID-19 infection since Shanghai lifted its lockdown on June 1.

At least 16 infections were found to have been to a supermarket in a commercial area, and another 15 were linked to a downtown barber shop.

Shanghai reported one locally transmitted COVID-19 asymptomatic infection outside of quarantine and lockdown communities on Monday.

On Sunday, the city registered 37 local infections, including 11 confirmed cases.

Most districts of the city screened residents with nucleic acid tests on the weekend, and the health authority said it will release the results soon.