After reporting an additional 4,000 new Covid cases, officials have locked down Shenyang, an industrial city of 9 million people.
Chinese health authorities recorded 4,770 new infections throughout the country on March 22, with most reported in the north-eastern province of Jilin.
In recent weeks China has imposed local lockdowns, mass testing and citywide closures.
It also reported two Covid-19 deaths on March 19, the first in over a year.
Officials say that 20,000 people have been infected in the resurgent Omicron wave.
Shenyang, an industrialized city and home to carmaker BMW, has prevented residents from leaving without proof of a 48-hour negative test result.
Also this week, Shanghai Disneyland resort closed again, as Covid case numbers continued to increase.
Currently, there are 37 million Chinese in lockdown.
Last week, Chinese health officials said that only half of the Chinese over 80 years old have been double-vaccinated.