Hundreds of flights at one of China's busiest airports were cancelled on Tuesday as Shanghai raced to bring a local coronavirus outbreak under control.

Health officials have tested thousands of staff at Pudong International Airport since a small clutch of Covid-19 cases in the city was linked to several cargo handlers.

The mainland – where the virus first emerged late last year – says it has largely brought the pandemic under control through travel restrictions and lockdowns, but it is now battling a number of domestic outbreaks in different cities.

Shanghai has reported seven local infections linked to the airport this month, with most cases found in the past few days.

The outbreak has sparked plans to give high-risk workers at the travel hub an experimental vaccine that Beijing has already been providing to state employees, international students and essential workers heading abroad since July.

On Tuesday, figures from data services firm VariFlight showed that over 500 flights out of Pudong Airport had been called off – nearly half the day's scheduled flights.

Almost half of scheduled inbound flights were also cancelled.

More than 17,700 people had been swabbed by Monday morning in the drive to test airport cargo staff, state news agency Xinhua reported.

Nearly half of all scheduled flights were also cancelled at Tianjin international airport, a northern port city also testing around 2.6 million people to try and bring a local cluster under control.

Tianjin reported five local cases on Saturday and another on Tuesday.

The mainland has been rolling out mass-screening campaigns in response to the emergence of local Covid-19 cases, in some cases collecting test samples from entire districts or cities.

Authorities have in recent days shifted their focus to imported frozen food and other inbound shipments, which have been blamed for a resurgence of local infections. (AFP)