The city of more than 20 million residents reported its first case in the latest outbreak on June 11. The infections were linked to the sprawling Xinfadi wholesale food center in the southwest of Beijing, which had until then reported no new cases for nearly two months.

In the 12 days since, 249 people have been infected in the worst outbreak in Beijing since the novel coronavirus was identified at a seafood market in the central Chinese city of Wuhan late last year.

Beijing can now administer more than 300,000 nucleic acid tests per day compared with 40,000 in March, Zhang Hua, deputy director at the Beijing Municipal Health Commission, told reporters.

Beijing took samples from 2.95 million people between June 12 and June 22, Zhang said.

"The strategy of Beijing's nucleic acid screening is mainly based on the level of risk and on severity," Zhang said, when asked if everyone in Beijing would be tested.

Testing will be done in batches and according to the profile of individuals, he said.

"We'll give priority to testing high-risk groups in Xinfadi and other markets involved in the outbreak as well as surrounding communities," Zhang said.

"On this basis, we've tested workers in restaurants, supermarkets, marketplaces, as well as residents in high-risk neighborhoods. Food delivery workers and parcel couriers have also undergone large-scale testing."