Shanghai authorities have promised some passenger and cargo services will continue operating as normal amid a new round of COVID-19 mass testing, with the city locked down in two phases starting on Monday.

"Although we have strict control measures, our airports, railways and international passenger and cargo services are operating normally," Wu Jinglei, director of the Shanghai Health Commission, said at a news briefing on Monday.

Under the testing strategy announced on Sunday, districts east of the Huangpu River will be locked down from 5 am Monday till 5 am Friday for the first phase of COVID-19 testing. The second phase will cover districts west of the river and run from 3 am Friday to 3 am April 5.

Businesses in locked down areas must enforce closed-loop management and allow employees to work from home. Buses, subways, ferries, taxis and online car-hailing services will be suspended during the lockdown. The restrictions will only apply to the half of the city under lockdown.

On Sunday, the city reported 3,500 new locally transmitted infections. Fifty have been confirmed as COVID-19 cases, with the rest asymptomatic.

Two areas earlier designated as medium risk－9 Jumenhou Road, Dapuqiao subdistrict in Huangpu district; and 760 Loutang Road, Jiading Industrial Zone, Jiading district－were downgraded to low risk on Monday.

"The grid screening the city has carried out over the past two weeks has revealed that the virus has spread in clusters across the city and there is a risk of further outbreaks. It's necessary to implement stricter measures now," said Wu Fan, a member of the team leading the city's COVID-19 prevention and control efforts, at the briefing.

"The new round of testing aims to reduce social mobility, identify infections, and eliminate the transmission of the virus in neighborhoods in order to protect people's lives and achieve zero spread outside virus transmission chains as soon as possible," she added.

To ensure a stable supply of daily necessities including food during the temporary lockdowns, the city will help local suppliers expand procurement channels, said Gu Jun, director of the Municipal Commission of Commerce.

"The city will issue certificates for enterprises dedicated to providing daily necessities, and guarantee their smooth operation," Gu said.

"Vehicles from those enterprises and with authorized permits issued by local government are allowed to operate across the city, including in areas that are under lockdown," he added.

The enterprises' employees will be allowed to enter and exit locked-down districts and their home neighborhoods as long as they hold relevant work and other permits, have a negative virus test within 48 hours of their activities, and a green health code clearance.

"We have also set up COVID-19 testing green lanes for employees of those companies," Gu said. "The city has an adequate supply of daily necessities, and measures have been taken to stabilize prices. We will try our best to meet residents' demands."

Wu Jinglei, director of the health commission, said that emergency departments, clinics that treat fevers, intensive care units, and maternity services at hospitals should remain operational. All hospitals are required to set up special lanes and quarantine wards for critically ill patients and make sure they receive timely treatment.

Residents who are not in critical condition but require regular medical treatment will be transferred to designated medical institutions through closed-loop transportation provided by their neighborhood committees.

The 10 central quarantine sites－h(huán)ospitals, exhibition halls, apartments and indoor stadiums－h(huán)ave been put into operation and medical personnel have been dispatched to these facilities, Wu said.