A city near Beijing that was rumored to be a test case for China dispensing with all virus restrictions has suspended schools, locked down universities and asked residents to stay at home for five days, a potential sign officials are reverting to tighter "COVID zero" curbs as cases multiply.

Shijiazhuang — a city of some 11 million people about 300 kilometers from the capital — has forbidden residents in areas deemed high risk from leaving their homes, with everyone else advised to stay at home "in principle,” according to the statement carried by the official Shijiazhuang Daily.

A mass COVID-19 testing exercise will be undertaken in six major districts, and universities will be put into so-called closed loops, where students are unable to leave campuses. All in-person classes at primary and middle schools have been halted.