The mainland's National Health Commission on Sunday reported another 824 domestic Covid-19 infections, with 157 symptomatic cases and 667 asymptomatic ones.

The majority of the cases were in Shanghai which added 622 infections, as well as three deaths involving people who had not been vaccinated against the virus.

The financial hub reopened four metro lines and 273 bus routes on Sunday and Zhao Dandan – deputy head of the city's health commission – said a phased reduction in anti-epidemic measures will be carried out.

“The first phase runs until May 31. As the number of new Covid infections continues to drop, the lockdown zones and controlled zones will be reduced,” Zhao said.

“The city will be split into different zones according to epidemic risk in the second phase. If the area contains no lockdown zones and controlled zones, it can be regarded as low-risk and the precautionary measures will be lifted.”

In Beijing, officials recorded 52 symptomatic infections and nine asymptomatic cases, while the port city of Tianjin saw 36 cases with symptoms and 20 without.