SHANGHAI (REUTERS) - The authorities in Shanghai have quarantined hundreds of people in an attempt to halt a fresh Covid-19 outbreak in the city after infections were detected in cargo workers at its airport, the municipal government said on Saturday (Aug 21).

Some 120 people deemed close contacts of the infected five workers at Pudong airport were placed in quarantine, along with hundreds of others deemed secondary contacts.

Two of the cargo workers, a Chinese national and an Ethiopian national, were included among four locally transmitted cases in mainland China's tally of 20 new confirmed infections for Aug 20, announced on Saturday.

Another two local cases were found in Jiangsu and Hubei provinces. Separate, unrelated outbreaks first emerged in those regions in July.

The national figure was down from 33 a day earlier, according to the National Health Commission, with locally transmitted infections steady at four.

Shanghai officials said later on Saturday that they had identified another three cargo workers at Pudong airport as confirmed cases.

China also reported 20 new asymptomatic coronavirus cases for Aug 20, all imported and unchanged from a day earlier.

China does not classify asymptomatic cases as confirmed infections.

No new deaths were reported. As at Aug 20, China had recorded 94,599 confirmed cases and 4,636 deaths.