BEIJING - The Chinese capital of Beijing in the past two weeks has been edging towards a state of alarm, as a flurry of Covid-19 cases in the city sparked mass testing, lockdowns of some residential areas, and caused mass gatherings and performances to be cancelled.

Some 18 locally transmitted cases, the first domestic infections in Beijing in over 150 days, have been detected since Dec 14.

City officials announced that Beijing was going into "emergency mode" on Sunday (Dec 27), and implemented escalating controls over the past few days.

Separate outbreaks have also been reported in northern Liaoning province's Dalian and Shenyang cities.

The spike in cases has caused concern in parts of Beijing, particularly in the Shunyi district where the Beijing Capital International Airport is located, that the virus may be circulating unseen in the capital.

The city on Tuesday completed mass testing of all Shunyi district residents, which turned up no new cases. Close to 1.3 million tests have been conducted in the district since last weekend.

Shunyi resident Tim Lin, who was screened for the virus on Sunday in the mass testing, told The Straits Times that residents were "definitely afraid".

"I think people are pretty anxious because there are quite a number of elderly people and young families living here," said the 37-year-old product designer, who added that his company had forbidden employees from coming to work unless they could present a negative nucleic acid test result.

The municipal government has announced that the situation in Beijing is "severe" and said residents need to be on high alert.

The latest spate of cases began almost two weeks ago when a Chinese national who arrived in Beijing from Hong Kong developed symptoms after he was released from quarantine on Dec 13.

Two cases linked to him were subsequently discovered.

Then, beginning last Wednesday, more cases began to be discovered including seven on Tuesday, mostly in the city's Shunyi district. So far, the cases do not appear to be linked to the man from Hong Kong.

As at Tuesday, 18 local transmissions have been recorded, according to data from the Beijing Centre for Disease Prevention and Control (CDC).

"The situation for epidemic prevention and control in Beijing is complex. We must be on high alert and strictly implement measures to prevent imported cases and a domestic rebound," Ms Pang Xinghuo, deputy director of the Beijing CDC said on Monday.

The authorities have put in place escalating curbs since the weekend.

Cinemas, tourist attractions and parks have been ordered to operate at 75 per cent capacity, and large performances and gatherings have been suspended. Primary and middle school students have had their winter vacations brought forward to earlier in January.

Some 10 villages, communities and buildings in Shunyi have also been sealed off, the authorities said at a press briefing on Tuesday, and civil servants have been told to remain in Beijing for the upcoming New Year and Chinese New Year holidays.

The state-run China Daily said in an editorial on Tuesday that while there was no need to panic, the city "seems to be facing a more challenging and seemingly more perilous situation, as the origin of many infections has yet to be traced".

But Chinese epidemiological experts have said it is unlikely that the virus was spreading widely in Beijing, as mass testing has so far not uncovered hidden cases.

Dr Jin Dong-Yan, a virology professor at the University of Hong Kong, pointed out that the seven cases reported on Tuesday were all close contacts of previous infections and not picked up through mass testing.

"The numbers are low. There is no sign the virus is spreading widely," said Dr Jin.

He pointed out that the Beijing authorities' language on the recent spate of cases - using terms like "emergency mode" and getting on a "war-footing" - seemed geared instead at jolting a populace fatigued by various social distancing measures back into action.

"The real concern is the coming holiday season, because a lot of people will be travelling, and if an infected individual goes undetected, there could be a real risk of a super-spreader event. The government's main task is to prevent this from happening," he said.