In China's locked-down commercial hub of Shanghai, new cases of the coronavirus have dropped below 3,000 for the first time in more than six weeks.

Shanghai authorities on Monday reported 2,858 new cases, most without symptoms.

The last time the daily tally was below 3,000 was on March 26, before outings were tightly restricted.

Meanwhile, social media users have been criticizing what they describe as forced isolation, in which residents are taken to a quarantine facility against their will just for living in condominiums with infected people.

A professor at a university in Shanghai who is an expert on the country's constitution posted on social media that forced isolation is illegal. The post was deleted and the professor's social media account was suspended.

Authorities explained at a news conference on Tuesday that people sharing kitchens or toilets in condominiums could be forcibly isolated.

But they added that risks would be determined on a case-by-case basis, apparently to deflect criticism.