A  medical worker collects sample to conduct nucleic acid test at a  sampling site in Shunyi District of Beijing, capital of China, Dec. 28,  2020. [Photo via Xinhua]

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.