China's commercial hub of Shanghai faces an unexpected round of mass Covid-19 testing for most residents this weekend – just 10 days after a city-wide lockdown was lifted.

Racing to stop a wider outbreak after discovering a few cases in the community, authorities have ordered PCR testing for all residents in 14 of Shanghai's 16 districts over the weekend.

Some districts said residents would not be allowed to leave their homes while the testing was carried out. A notice issued in Changning district described the stay home requirement as “closed management” of the community being sampled.

The reactions of people on the Weibo platform were a mixture of surprise and concern, with some asking how their plans for the weekend, such as moving house or seeing a doctor, would be affected.

The move comes on top of testing requirements that Shanghai introduced for its 25 million residents after easing a city-wide lockdown on June 1. Residents need to prove that they have been tested within the last 72 hours to enter areas like malls and offices – or even to use subways and buses.

Some parts of Shanghai had remained under or returned to lockdown shortly after June 1 due to positive cases and their close contacts. Three of the latest infections that led to several closures were traced to a popular beauty salon in the city centre.

In Beijing, officials have shut entertainment and internet venues in two of the capital's largest districts after tracing cases to a few bars.

Meanwhile, President Xi Jinping has said the zero-Covid policy must be maintained.

Xi on Thursday called for "efficiently coordinating Covid-19 prevention and control with economic and social development", according to Xinhua news agency. He added China's "dynamic zero-Covid approach must be unswervingly upheld".

Nationally, there were 73 new local coronavirus cases for June 9, of which 30 were symptomatic and 43 had no symptoms.

Of the symptomatic cases, 15 were from Inner Mongolia, seven from Beijing and six were found in Shanghai.

There were five asymptomatic cases in Shanghai and one in Beijing. (Reuters/AFP)