Shanghai reported six locally transmitted COVID-19 infections outside of quarantined and locked down communities on Thursday, including three working at a downtown barber shop in Xuhui district.

The six infections, including five confirmed cases, lived in the city's Baoshan, Minhang and Xuhui districts.

As of 4 pm Thursday, 655 close contacts and 1,230 secondary close contacts of the cases have been traced and put under quarantine. All their nucleic acid test results so far are negative, Zhao Dandan, deputy director of the Shanghai Health Commission, said at a press briefing.

"Since June 1, when Shanghai lifted most epidemic prevention and control measures, scattered infections have emerged continuously, especially in old neighborhoods and service venues," Zhao said.

"There still exists the risk of an epidemic rebound, and all the city's residents should abide by strict personal protection protocols at public venues and the service industry must work under rigorous management," he said.

Wang Hongwei, vice-governor of Xuhui district, said the shop has 16 employees and has traced 481 customers potentially at risk.

"We'll further require all service venues to receive customers with valid nucleic acid test results taken within 72 hours and normal body temperature. All workers and customers must wear masks throughout the process. Shops must also provide service upon reservation and ensure the customers' information is traceable," he said.

Massive nucleic acid tests will be carried out on the weekend in Pudong, Huangpu, Jing'an, Xuhui, Hongkou, Baoshan, and Minhang districts, which have reported infections since June 1, said the health authority, and lockdown will be imposed throughout the testing period.