Beijing has reported its highest number of Covid-19 cases in 18 months, five days ahead of the start of the Winter Olympics in the Chinese capital.
After 20 more cases were reported in the capital, officials announced that some local areas had been locked down with residents being tested.
Separately, organisers of the Olympics reported 34 new infections within the event's "closed-loop" bubble.
Officials said it included 13 athletes or officials arriving at the airport.
Anyone testing positive is being put into isolation and only allowed to compete after getting two negative test results in 24 hours.
The Winter Olympics are going ahead despite travel in and out of China being severely restricted since the pandemic began.
Those travelling to Beijing for the games must come on charter flights and stay in their bubble until they leave.
People have to clear Covid-19 tests before and after arriving in China, with tens of thousands inside the bubble also undergoing daily testing as well as being expected to wear masks.
The country's National Health Commission (NHC) reported 20 new cases in Beijing on Sunday - the highest number since June 2020.
Local officials have locked down housing compounds in the Fengtai district - where many of the cases were recorded. Some 2 million people will be tested for the virus in response, AFP news agency reports.
The NHC reported 54 new cases in total nationwide on Sunday, including cases in the eastern city of Hangzhou and Suifenhe in Heilongjiang province.
The virus was first detected in the Chinese city of Wuhan in late 2019 before spiralling into a global pandemic.
China has maintained a zero-Covid policy since the first outbreak, with local transmission met with harsh restrictions and widespread testing to stop the spread.
The country has reported about 120,000 cases and 4,600 coronavirus deaths since - much lower than the figures reported by other major nations.