“Shanghai’s epidemic prevention and control is at the most difficult and most critical stage,” Wu Qianyu, an official with the municipal health commission, told a briefing.

“We must adhere to the general policy of dynamic clearance without hesitation.”

Shanghai’s quarantine policy has already been criticised for separating children from parents and putting asymptomatic cases among those with symptoms. Ms Wu did not comment on the uproar over family separations. Earlier she insisted that children who tested positive had to be kept apart.

The city has set up about 47,700 beds in a number of newly built temporary hospitals in Shanghai, with another 30,000 being readied, state news agency Xinhua reported on Tuesday.

A total of 62 temporary quarantine sites have been designated elsewhere.

Residents under lockdown in their homes have complained of problems with food deliveries since the reintroduction of widespread restrictions last week after the city initially took a more targeted approach.