Beijing reported 51 new locally transmitted COVID-19 cases between 3pm Tuesday and 3pm on Wednesday, bringing the total number of infections to 1,642 since April 22. Sixteen districts are involved, Liu Xiaofeng, deputy director of the Beijing Center for Disease Prevention and Control, said at a news conference on Wednesday afternoon.

"Of the new infections, 47 were reported in quarantine locations and four were found from mass nucleic acid tests at community level," he said.

Of all 1,642 cases, Chaoyang district registered 417 cases, the most in the outbreak, followed by Fangshan, which reported 412. Fengtai reported 346 and Haidian reported 214.

As of Wednesday, Beijing had nine high-risk areas for COVID-19 and 21 medium-risk areas.

"Two patients who were supposed to be quarantined at home have been to supermarkets and workplaces, which added to the risk of infection," Liu said. "The epidemic control and prevention work is at a critical stage at present, and we should take faster action and stricter measures to cut transmission."

"We thank all residents who have been following prevention measures such as staying at home and taking nucleic aid tests on time," he said.

Beijing conducted nucleic acid tests for 16.39 million residents on Tuesday and one tube showed a positive result in Dongcheng district, according to Zhong Dongbo, deputy head of the Beijing Health Commission.