XI'AN -- Northwest China's Shaanxi province has reported a total of 651 locally transmitted confirmed COVID-19 cases from Dec 9 to Sunday, in the latest resurgence.

Of the total, 635 cases were reported in Xi'an, the provincial capital, Zhang Bo, deputy director of the Xi'an municipal health commission, told a press briefing Monday.

On Sunday, the province reported 152 local COVID-19 cases, with 150 in Xi'an. Of the 150 in the city, 67 were found through mass nucleic acid testing and 82 were found among those in quarantine in designated places, while the remaining case was detected when the person sought medical help, Zhang said.

Local authorities will strive to contain COVID-19 in the shortest time with the help of lockdown measures and the support of local residents, said Ma Guanghui, deputy director of the provincial health commission.

The province has placed 16,798 close contacts of the cases and 34,291 secondary close contacts under medical observation.

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

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

The provincial center for disease control and prevention has finished the whole genome sequencing of 137 cases and found they are highly homologous with imported cases aboard an inbound flight on Dec 4.