Xi'an, capital of northwest China's Shaanxi Province, reported 175 confirmed locally transmitted COVID-19 cases on Monday, bringing to 811 the total number of local cases in the latest resurgence since Dec. 9.

Of the 175 new cases, 69 were found through mass nucleic acid testing and 105 were found among those in quarantine in designated places, while the remaining case was detected when the person sought medical help, according to a press briefing held by the Xi'an municipal government on Tuesday.

Health authorities in the city launched the fifth round of mass nucleic acid testing at noon on Monday in a bid to weed out as many infections as possible.

As of Tuesday noon, more than 12.3 million people had been tested with the help of 5,077 sample collecting venues and more than 31,000 sample collectors.

To screen for more infections, health authorities in three districts of Xi'an will carry out all-inclusive nucleic acid testing once each day starting Tuesday.

Authorities in Xi'an have upgraded epidemic control and prevention measures starting Monday, ordering all residents to stay indoors and refrain from gatherings except when taking nucleic acid tests.