China’s capital Beijing has closed some public spaces and stepped up checks at others as most of the city’s 22 million residents embark on more COVID-19 mass testing aimed at averting a Shanghai-like lockdown.

As Beijing rolled out three rounds of mass testing this week across a number of districts, it locked down residential compounds, office blocks and a university after infections were found.

Some schools, entertainment venues and tourist sites were also shuttered.

Universal Studios in Beijing announced late on Wednesday it would require visitors to show negative test results before they could enter the theme park, starting on Friday.

Across Beijing, positive cases were found among the nearly 20 million samples acquired in the first round of mass testing, but numbers remained low.

The city on Thursday reported 50 new infections for April 27, up from 34 a day earlier.

Since April 22, Beijing has found more than 160 cases, more than half in Chaoyang, the city’s most populous district known for its nightlife, malls and embassies.

Despite the low caseload, Beijing remained on edge.

Officials in Yanqing, a small district in the north of the city with a population of 350,000, said on Thursday they will start screening those who live and work in the area, even though it is not on the list of districts ordered to conduct mass testing this week.

When the outbreak in Shanghai began, new infections were below 100 a day between March 1 and 10, before doubling and then surging to more than 700 by March 20.

By the end of March, Shanghai was reporting thousands of new infections, prompting a citywide lockdown and upending the lives of its 25 million residents.

So far, Beijing has tried to avoid disrupting its economy, allowing residents to go to work even as they get tested, unless infections are found and localised lockdowns are required.

“We’ll have to stay at the dormitory first, then come back to work after the lockdown is lifted,” said a migrant worker surnamed Wu, who arrived in Beijing on Wednesday after a 10-hour train journey with a friend.

The two were to begin work in a canteen of the Beijing University of Technology, but that did not happen after residential compounds next to the university went into lockdown.

After a long discussion with staff at the university, they were told to stay at a dormitory currently under lockdown.

“We can cook in the dormitory, and I’m sure it’s only a matter of time until the lockdown is lifted,” Wu said.

“I won’t ask for money if I don’t work.”