Around 21 million people have been ordered to stay in isolation in China after an outbreak of coronavirus cases, the BBC reported on Thursday.
The new regulation has determined that only one person per family is allowed to go out to buy basic things.
On Thursday, the city of Chengdu recorded 157 new infections, prompting strict lockdowns in the region.
China's COVID policies require cities to go into quarantine even if only a small fraction of cases are reported.
Chengdu residents, who were told to stay at home from 18pm local time on Thursday, will all be tested over the next few days, but it was not clear when the restrictions would be lifted.
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Meanwhile, people have been banned from entering or leaving Chengdu.
Other restrictions are currently in place elsewhere in China, including Shenzhen in the south and Dalian in the north-east.
