People wearing face masks walk along a street in Beijing on November 19, 2020. (Photo: AFP)

BEIJING, Dec. 28 (Xinhua) -- Beijing has expanded its nucleic acid testing and tightened COVID-19 prevention and control measures following new reports of local COVID-19 infections, local authorities said on Monday.

The city faces a grim and complicated situation with risks of further infections still present, said Xu Hejian, a spokesperson for the Beijing municipal government, at a press briefing.

Several locally transmitted cases have recently emerged in Chaoyang, Xicheng and Shunyi districts of Beijing, again sounding the alarm for COVID-19 prevention and control.

Shunyi District is expanding its nucleic acid testing and has entered a coronavirus "wartime state," with tightened personnel flow management and mass testing in progress. A total of 891 close contacts of confirmed and asymptomatic cases, and 618 close contacts of those 891 people have been identified and placed under medical observation.

The district has carried out nucleic acid testing for 1,207,657 people as of 3 p.m. Monday, and samples taken from 901,206 people have returned negative, according to Shunyi official Zhi Xianwei.

To beef up COVID-19 control at entry points, Beijing customs have since Sept. 3 implemented quarantines for 4,735 flights as of Sunday, including 188 international flights.

During the upcoming New Year and Spring Festival holidays, supplies of daily necessities in Beijing will be guaranteed, said Wang Hongcun with the Beijing Municipal Commerce Bureau.