Truck entry into the port area remains restricted while some container freight stations have halted operations due to roadblocks and other lockdown measures in the city's Beilun District, home to a string of large box terminals, reports UK's Lloyd's List.

The latest infection wave, which emerged on January 1, has so far been contained within the district, where 26 local cases were confirmed on January 4. Most of them are from a workshop of a clothing company named Shenzhou International, the Ningbo government told a press conference.

Among over 20,000 local container truck drivers, only 6,000 some had received special passes to enter and leave the port via five designated routes, according to the latest available government update.

Delays of shipments are inevitable due to the traffic control, said a local freight forwarder.

"Also, some truck drivers trapped in the lockdown area are unable to apply for the passes. Some are reluctant to go to Beilun and the terminals now deemed as a Covid risky area that can invoke quarantine requirement in other cities."

Some warehouses and factories have also halted the pickup and delivery of cargo amid the restrictive rules, he added.

"The impact is worse because we are now in the peak season for exports ahead of the Chinese New Year."

The situation has raised concerns over deteriorating port congestion in the region, where pilots are also in short supply owing to separate Covid cases confirmed in other cities along the Yangtze River.

Outside of Shanghai and Ningbo-Zhoushan, figures from Lloyd's List Intelligence show that 120 ships comprising 613,713 TEU are still at anchor off the two ports on January 4.

That is higher than the levels seen in mid-August when a major terminal in Ningbo's Meishan Island was shut down for several weeks because of a dockworker contracting coronavirus.

Jiang Yipeng, a senior executive at Ningbo-Zhoushan Port, which handled more than 30 million TEU last year, said the port is revving up efforts to cope with the challenge.

The port handled over 97,000 TEU of containers a day between January 1-3, an increase of 8.5 per cent compared with the year-earlier period, he said.