Beijing reported two new asymptomatic COVID-19 cases by 4 pm on Thursday, according to the city's epidemic control authorities.

"Beijing faces a complicated situation in terms of virus control and prevention. People under centralized or home-based medical observation should obey the regulations strictly and not go out," Pang Xinghuo, deputy head of the Beijing Center for Disease Control and Prevention, said at a news conference on Thursday afternoon.

Residents who have received nucleic acid tests should not leave the city before they have received their results, she stressed.

One of the two new cases involves a 34-year-old man surnamed Fu, who is a resident of Beijing's Shunyi district. His positive result came when he was in Ningbo, Zhejiang province. He had flown from Beijing to Ningbo on flight CA8347 on Tuesday evening with three colleagues for a business trip. His three colleagues all tested negative. Fu has been transferred to a hospital in Ningbo for isolation and observation.

The Lianzhuhuayuan residential community in Shunyi district, where Fu lives, has been closed to outsiders. How and when he got infected remains under investigation.

The other case in Beijing involves a man in Xicheng district's Financial Street area who works in cold-chain business at a supermarket. He came to Beijing on Dec 6 from Tianjin and took a nucleic acid test as required by the city for employees of businesses such as restaurants and supermarkets.

All close contacts of the two cases have been identified and put under medical observation.

In Shunyi, 1,970 residents in Fu's community and 3,755 people at his workplace in Haidian district have been tested for COVID-19 and all were negative.

And 80 close contacts of the man in Xicheng received nucleic acid tests, and their results were all negative, according to health authorities.

Weekly mass testing will also be launched in Xicheng for workers at restaurants and cold-chain businesses.

Meanwhile, in Liaoning province, 3.44 million residents of Dalian had been tested by noon on Thursday. So far, 1.37 million samples had been tested, and all available results were negative, according to the city's health commission.

Shenyang, capital of Liaoning, also reported a new asymptomatic case on Thursday, the husband of the city's latest confirmed patient, a 67-year-old woman who had recently returned from South Korea, according to the city's health commission.

Two residential communities related to the case have been classified as medium-risk for COVID-19.

As of Wednesday, Liaoning had 13 confirmed cases and 23 asymptomatic cases, according to the provincial health commission.

Wu Yong in Shenyang contributed to this story.