The COVID-19 situation in Shanghai has hit a plateau as daily cases fluctuate and the death toll rises, local health authorities said on Sunday.

Shanghai reported 39 new COVID-19 related deaths on Saturday, three times more than the number of deaths on Friday and also the highest daily toll as the city is battling with China's biggest coronavirus outbreak. 

The 39 people who died, averaging 78.7 years old, all had serious chronic diseases, including coronary heart disease and hypertension. None of them had received COVID-19 vaccines, the health officials said at a daily news conference.

"The number of severe and critically ill COVID-19 cases has increased in recent days, and the positive patients with underlying medical conditions, especially the elderly, are at higher risk of developing into severe cases and even dying," said Zhao Dandan, deputy director of the Shanghai Municipal Health Commission.

"So the elderly eligible for taking COVID-19 vaccines should be vaccinated as soon as possible," Zhao added.

The eastern Chinese megacity, home to 25 million people, reported 1,401 confirmed locally transmitted COVID-19 cases and 19,657 local asymptomatic carriers on Saturday, respectively down from 2,736 and 20,634 reported on Friday.

"Based on recent data, the number of newly added positive cases are still high and fluctuating, and the patients are mainly from several construction sites and enterprises, which have resumed their production activities recently," said Zhao, adding that, "it's still necessary to realize the severity and complexity of the pandemic situation in Shanghai."

"To control infectious disease, the basic principle is to control the source of infection, cut off the way of transmission, and protect the susceptible population," Zhao said.

In the future days, Shanghai will continue carrying out combined antigen plus nucleic acid tests in communities under closed-off management as well as in controlled and prevention areas, Zhao said.

The Chinese mainland recorded 1,566 locally transmitted cases and 20,285 new asymptomatic cases on Saturday.

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