Shanghai on Monday implemented a new regulation requiring all inbound visitors or residents returning from other provinces to undergo one nucleic acid test every day for three days upon arriving.

The new regulation comes on the back of the discovery of several new infections outside the city's quarantined population over the past week. Most of the cases are inbound visitors or returning residents.

To curb the spread of the virus, the city has also required all residents to be screened for COVID-19 twice a week till early November.

Shanghai reported four confirmed cases and 24 asymptomatic infections on Monday, said the city's health commission. One confirmed case and one asymptomatic infection were found outside its quarantined population.