Beijing warned over the weekend that Covid had spread undetected in the city for a week and that more cases would be found.
Anyone living or working in the main business district of the region will be tested over the next three days. The district accounted for most of the new Covid cases in Beijing.
Beijing has only a few apartment buildings that have been locked down. All in-person group activities and training courses were stopped by the business district.
The Covid outbreak in mainland China is the worst since early 2020. The country has stuck to a strict zero- Covid policy of using swift lockdowns and travel restrictions to control the spread of the virus.
More than 100 new Covid-related deaths have been reported in the city since Friday.
More than 2,400 cases with symptoms and more than 16,000 without were reported by the city of Shanghai.
According to Wind Information, Beijing and Shanghai are among China's ten largest provincial-level regions. The data shows Beijing's economy grew by 4.8% in the first quarter, the same as the national level, and Shanghai's economy grew by 3.1% in March.
Service industry workers affected by the latest round of cases in Beijing can receive a maximum of 21 days of compensation, according to the municipal authorities.
Locals rushed to stock up on food after hearing of the spike in cases.