Sichuan province accounted for 128 of the 318 locally-transmitted Covid-19 cases reported on the mainland on Thursday.
The provincial capital of Chengdu on Thursday announced a lockdown of its 21 million residents and four days of citywide testing.
Residents there were told to stay home and about 70 percent of flights in and out of the city were suspended.
Guangdong, meanwhile, recorded 55 locally-transmitted cases, with entertainment venues shut down in Shenzhen after infections were reported there.
The National Health Commission also reported 1,567 local asymptomatic infections across the mainland for the day.
There were no new deaths, keeping the tally steady at 5,226. (Agencies)